Method for manufacturing battery material

Abstract

To provide a method for manufacturing a battery material which leaches much valuable metal and is highly efficient.SOLUTION: The method for manufacturing a battery material disclosed herein includes: a preparation step of preparing a recovery target containing at least one of Ni and Co as metal valuable; a heating step of heating the recovery target at temperatures of at least 500°C so that at least a part of the valuable metal is reduced to a metal state alone; an ammonia leaching step of immersing the recovery target after the heating step in an ammonia solution in which ammonia, a pH buffer agent, and an oxidant are mixed and obtaining a metal solution containing valuable metal.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The technology disclosed herein relates to a method for producing battery materials. [Background technology]

[0002] Lithium ion secondary batteries are widely used in various fields. Various materials including valuable metals such as Ni and Co are used in these lithium ion secondary batteries. For example, the positive electrode plate of a lithium ion secondary battery includes a positive electrode active material and a positive electrode core. For the positive electrode active material, lithium transition metal composite oxides such as lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, and lithium nickel cobalt manganese composite oxide are used. Furthermore, aluminum or the like is generally used for the positive electrode core.

[0003] In recent years, development of recovery technology for recovering valuable metals from used batteries and process scraps and reusing them as battery materials has been progressing. For example, Patent Document 1 and Non-Patent Document 1 are examples of recovery technology for positive electrode plates. Patent Document 1 discloses a valuable metal recovery method including a heating step of heating battery slag (recovery target) having a positive electrode active material containing Ni and / or Co and a negative electrode active material containing graphite to oxidize graphite contained in the negative electrode active material in the battery slag to generate carbon dioxide gas, an acid leaching step of leaching Ni and / or Co into sulfuric acid to generate a leaching solution, and a recovery step of recovering Ni and / or Co. Patent Document 1 discloses that valuable metals (Ni ions and Co ions) in the recovery target are reduced to divalent oxides. Non-Patent Document 1 also discloses that positive electrode scraps are prepared by crushing positive electrode plates, and the positive electrode scraps are subjected to ammonia leaching. In such ammonia leaching, ammonia-ammonium sulfate is used as the leaching solution, and sodium sulfite is used as the reducing agent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-118594 A [Non-patent literature]

[0005] [Non-Patent Document 1] Waste Management Volume 60, February 2017 Pages 680-688 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, in a typical valuable metal recovery method, valuable metals are heated and leached in an acid solution such as sulfuric acid. However, when the acid leaching step is carried out, the valuable metals are recovered as sulfates through a neutralization step and a solvent leaching step, as disclosed in Patent Document 1, and the recovered valuable metal sulfates are used to manufacture battery materials such as positive electrode active materials. Such recovery methods tend to involve many steps and are cumbersome.

[0007] An alkaline solution (particularly aqueous ammonia) is used when producing a positive electrode active material. As a result of the inventors' investigations, they found that by performing ammonia leaching when recovering valuable metals (e.g., Ni and / or Co), a positive electrode active material can be produced without performing the conventional neutralization step or solvent leaching step. On the other hand, the ammonia leaching method disclosed in Non-Patent Document 1 has a slow dissolution rate of Co in particular, and takes more than 240 minutes to reach a leaching rate of over 80%, which is undesirable from the viewpoint of production efficiency.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a battery material which has a high leaching rate of valuable metals and is highly efficient. [Means for solving the problem]

[0009] In order to solve the above problems, a method for producing a battery material (hereinafter, also simply referred to as a "production method") having the following configuration is provided.

[0010] The method for producing a battery material disclosed herein includes a preparation step of preparing a recovery target containing at least one of Ni and Co as a valuable metal; a heating step of heating the recovery target at 500°C or higher so as to reduce at least a portion of the valuable metal to an elemental metal state; and an ammonia leaching step of immersing the recovery target after the heating step in an aqueous ammonia solution containing ammonia, a pH buffer, and an oxidizing agent to obtain a metal solution containing the valuable metal.

[0011] In the manufacturing method having the above configuration, a high leaching rate can be achieved in a short time in the ammonia leaching step by heating so as to reduce at least a part of the valuable metal to the elemental metal state. Furthermore, in the manufacturing method having the above configuration, since an acid leaching step is not performed, a neutralization step or other step does not need to be performed. Therefore, according to this configuration, a manufacturing method for a battery material having a high leaching rate of valuable metals and high efficiency is realized. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a vertical cross-sectional view that illustrates a schematic internal structure of a lithium-ion secondary battery. [Diagram 2] FIG. 2 is a perspective view that typically shows an electrode assembly of the lithium ion secondary battery shown in FIG. [Diagram 3] FIG. 3 is a flow chart illustrating a method for producing a battery material according to one embodiment. [Figure 4] FIG. 4 is a flow chart illustrating in detail the heating step in the manufacturing method according to one embodiment. [Diagram 5] FIG. 5 is a flow chart illustrating in detail the ammonia leaching step in the manufacturing method according to one embodiment. [Figure 6] FIG. 6 shows the results of XRD analysis in Example 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the drawings. Note that matters other than those specifically mentioned in this specification and necessary for implementing the technology disclosed herein can be understood as design matters for a person skilled in the art based on the prior art in the field. The technology disclosed herein can be implemented based on the contents disclosed in this specification and common technical knowledge in the field.

[0014] 1. Items to be recalled The method for producing a battery material according to the present embodiment produces a battery material (typically, a material for a positive electrode active material of a lithium ion secondary battery, a precursor of the positive electrode active material, or a positive electrode active material) by recovering valuable metals such as Ni and Co from a predetermined recovery target. An example of the recovery target here is a used lithium ion secondary battery. Hereinafter, this lithium ion secondary battery will be specifically described. FIG. 1 is a vertical cross-sectional view that typically shows the internal structure of a lithium ion secondary battery. FIG. 2 is a perspective view that typically shows an electrode body of the lithium ion secondary battery shown in FIG. 1.

[0015] As shown in FIG. 1, the lithium ion secondary battery 1 includes a case 10, an electrode assembly 20, and an electrolyte (not shown).

[0016] (1) Case The case 10 is a box-shaped container. An electrode body 20 and an electrolyte are housed inside the case 10. For example, a metal material (such as aluminum (Al)) having a certain strength is used for the case 10. A positive electrode terminal 12 and a negative electrode terminal 14 are attached to the case 10. The positive electrode terminal 12 and the negative electrode terminal 14 are connected to the electrode body 20 inside the case 10. Specifically, the positive electrode terminal 12 is connected to a positive electrode plate 30 (see FIG. 2) of the electrode body 20. The positive electrode terminal 12 is made of aluminum (Al) or the like. On the other hand, the negative electrode terminal 14 is connected to a negative electrode plate 40 (see FIG. 2) of the electrode body 20. The negative electrode terminal 14 is made of copper (Cu) or the like.

[0017] (2) Electrode body The electrode body 20 is a power generating element of the lithium ion secondary battery 1. As shown in Fig. 2, the electrode body 20 includes a positive electrode plate 30, a negative electrode plate 40, and a separator 50. The electrode body 20 shown in Fig. 2 is a wound electrode body. This wound electrode body is produced by stacking the positive electrode plate 30, the negative electrode plate 40, and the separator 50 to form a long strip-shaped laminate, and then winding the laminate. However, the structure of the electrode body 20 is not particularly limited, and may be any other conventionally known structure (such as a laminated electrode body).

[0018] The positive electrode plate 30 includes a positive electrode core 32, which is a metal foil having electrical conductivity, and a positive electrode active material layer 34 applied to the surface of the positive electrode core 32. Aluminum (Al) or the like is used for the positive electrode core 32. The positive electrode active material layer 34 is a composite layer containing a positive electrode active material, a conductive material, a binder, and the like. The positive electrode active material is a lithium transition metal composite oxide containing at least one of nickel (Ni) and cobalt (Co). Examples of such lithium transition metal composite oxides include lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel manganese composite oxide, lithium manganese cobalt composite oxide, lithium nickel cobalt composite oxide, and lithium nickel manganese cobalt composite oxide. According to the manufacturing method of this embodiment, Ni and / or Co can be efficiently recovered from a recovery target containing such a lithium transition metal composite oxide. Examples of the conductive material include carbon materials such as acetylene black and graphite. Examples of the binder include resin materials such as polyvinylidene fluoride (PVdF).

[0019] The negative electrode plate 40 includes a negative electrode core 42, which is a metal foil having electrical conductivity, and a negative electrode active material layer 44 applied to the surface of the negative electrode core 42. The negative electrode core 42 is made of copper (Cu) or the like. The negative electrode active material layer 44 is a composite layer containing a negative electrode active material, a binder, a thickener, and the like. Examples of the negative electrode active material include carbon materials such as graphite, hard carbon, and soft carbon. Other examples of the negative electrode active material include lithium titanate (LTO), silicon carbide, a composite containing carbon and silicon, and silicon oxide (SiO X) and the like. Although the details will be described later, according to the manufacturing method of this embodiment, even when a battery using such a non-carbon-based negative electrode active material is to be collected, the recovery efficiency of valuable metals can be appropriately improved. In addition, examples of binders include resin materials such as styrene butadiene rubber (SBR). Examples of thickeners include resin materials such as carboxymethyl cellulose (CMC).

[0020] The separator 50 is an insulating sheet interposed between the positive electrode plate 30 and the negative electrode plate 40. For example, a resin material such as polyethylene (PE), polypropylene (PP), polyester, cellulose, or polyamide is used for the separator 50. A heat-resistant layer containing an inorganic filler may be formed on the surface of the separator 50. Examples of such inorganic fillers include inorganic oxides such as aluminum oxide, magnesium oxide, silicon oxide, and titanium oxide; nitrides such as aluminum nitride and silicon nitride; metal hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide; and clay minerals such as mica, talc, boehmite, zeolite, apatite, and kaolin.

[0021] (3) Electrolyte The electrolyte is present between the positive electrode plate 30 and the negative electrode plate 40. This allows charge carriers (Li ions) to move between the positive electrode plate 30 and the negative electrode plate 40. Examples of the electrolyte include a non-aqueous electrolyte solution and a gel electrolyte. Note that the electrolyte may be any electrolyte that can be used in a lithium ion secondary battery without any particular limitation, and does not limit the technology disclosed herein.

[0022] The lithium ion secondary battery 1 has been described above as an example of a collection target in the manufacturing method according to the present embodiment. However, the manufacturing method disclosed herein is not limited to only a method in which the lithium ion secondary battery 1 having the above configuration is the collection target. For example, at a manufacturing site of a lithium ion secondary battery, a part of a positive electrode plate may be cut off when an electrode body is manufactured. This cut part of the positive electrode plate (process waste material) may also contain Ni and Co, and therefore may be a collection target in the manufacturing method disclosed herein. In addition, at a manufacturing site of a lithium ion secondary battery, some defect may occur in the electrode body after manufacture, and it may become unusable in a product. Such an electrode body may also be a collection target because it may contain Ni and Co. In other words, the collection target in the manufacturing method disclosed herein may contain at least one of Ni and Co, and is not particularly limited to a specific structure.

[0023] 2. Manufacturing method of battery materials The manufacturing method of the battery material according to this embodiment will be described below. Fig. 3 is a flow chart for explaining the manufacturing method according to this embodiment. Fig. 4 is a flow chart for explaining in detail the heating step in Fig. 3.

[0024] 3, the method for producing a battery material according to this embodiment includes a preparation step S10, a heating step S20, and an ammonia leaching step S30. The method for producing a battery material disclosed herein may further include a precursor preparation step S40 and an active material production step S50. Each step will be described below.

[0025] (1) Preparation process S10 In the preparation step S10, a recovery target containing at least one of Ni and Co as a valuable metal is prepared. As described above, the "recovery target" in the technology disclosed herein may contain at least one of Ni and Co as a valuable metal. In other words, the recovery target is not limited to completed lithium ion secondary batteries, but includes process scraps and defective parts (electrode bodies, etc.). Details of the recovery target have already been described, so a duplicated description will be omitted.

[0026] (2)Heating process S20 In the heating step S20, the prepared recovery target is heated to 500°C or higher. In the recovery target prepared in the preparation step S10, valuable metals (Ni, Co) exist in the state of divalent or trivalent metal ions. By heating at least 500°C or higher in the heating step S20, at least a portion of these valuable metals can be suitably reduced to the state of elemental metals (metal Ni, metal Co). This can improve the recovery efficiency of valuable metals (Ni and / or Co) in the ammonia leaching step S30 described later.

[0027] In the heating step S20, when the recovery target contains Ni, it is preferable to heat at 500°C or higher so that at least a part of the Ni is reduced to a metallic Ni state. In addition, in the heating step S20, when the recovery target contains Co, it is preferable to heat at 500°C or higher so that at least a part of the Co is reduced to a metallic Co state. In addition, in the heating step S20, when the recovery target contains both Ni and Co, it is preferable to heat at 500°C or higher so that at least a part of the Ni and Co is reduced to a metallic Ni and metallic Co state. In the manufacturing method disclosed herein, it is sufficient that a part of the valuable metal in the recovery target after calcination is reduced to a simple metal state, and a part may exist in an oxide state.

[0028] In the heating step S20, the prepared collection target is heated to remove liquid components (electrolyte, etc.) in the collection target and carbonize resin components (binder, separator, etc.). When a charged lithium ion secondary battery 1 is to be collected, the heating step S20 can be performed to stop the battery function. This allows the subsequent steps to be performed safely. Although not particularly limited, the heating step S20 may include a measurement step S21, a determination step S22, a reducing component addition step S23, a firing step S24, and a selection step S25, as shown in FIG. 4. The steps will be described in detail below.

[0029] (a) Measurement process S21 In the measurement step S21, the amounts of oxygen element (O) and reduced components contained in the collection target are measured. In the measurement step S21, a part of the collection target is taken as a measurement sample, and the oxygen element and reduced components of the measurement sample are measured. Furthermore, the measurement step S21 only needs to be performed when the type of collection target is changed, and does not need to be performed on all of the prepared collection targets. This can improve production efficiency.

[0030] In this specification, the "reducing component" is not particularly limited as long as it is a component capable of reducing Ni and Co in the firing step S24 described later. In the manufacturing method disclosed herein, carbon element (C) can be preferably used as the reducing component. Carbon can be particularly preferably used as the reducing component from the viewpoint that it is not easily oxidized and is stable until the firing step S14 is started. In addition, depending on the type of the object to be recovered, various carbon materials (conductive materials, binders, negative electrode active materials, etc.) may be contained. By using these carbon materials as a supply source of the reducing component, it is possible to contribute to reducing the cost required for recovering valuable metals.

[0031] The means for measuring the amount of substance of the reduced component (carbon element) in the recovery target is not particularly limited, and any conventionally known measuring means can be used without particular limitation. For example, means for measuring the amount of substance of carbon element include thermogravimetric differential thermal analysis (TG-DTA), SEM-EDS analysis, oxygen flow combustion-non-dispersive infrared analysis, and combustion volume method.

[0032] Next, a method for measuring the amount of substance of the oxygen element in the object to be recovered will be described. First, when the chemical composition of the positive electrode active material in the object to be recovered is known in advance, it is advisable to measure the amount of substance of the metal element in the object to be recovered and calculate the amount of substance of the oxygen element based on the amount of substance of the metal element. This makes it possible to easily measure the amount of substance of the oxygen element in a valuable metal oxide (for example, a lithium transition metal composite oxide). A specific example of such a measurement procedure is as follows. First, a solution is prepared by dissolving a part of the object to be recovered (a measurement sample) in an acid. Next, an inductively coupled plasma analysis (ICP) is performed on this solution. This makes it possible to measure the total amount of substance M of the transition metal elements (Ni, Co, Mn) in the object to be recovered. Then, the chemical composition of the positive electrode active material in the object to be recovered (LiNi x Co y Mn z O δ ) is known, the ratio (x+y+z:δ) of the total amount of substance of the transition metal elements (x+y+z) to the amount of substance of O (δ) can be obtained. In this case, the amount of substance N of the oxygen element can be calculated from the ICP measurement results (total amount of substance M of the metal elements) based on the following formula (1). N = δ M / (x + y + z) (1)

[0033] The means for measuring the amount of substance of the oxygen element in the object to be recovered is not limited to the above means, and any conventionally known measuring means can be used without any particular limitation. For example, the oxygen element in the object to be recovered may be directly measured using SEM-EDS analysis, XRF analysis, etc. By using these methods, the amount of substance of the oxygen element can be measured even if the chemical composition of the positive electrode active material in the object to be recovered is unknown.

[0034] (b) Judgment step S22 In the judgment step S22, it is judged whether the amount of substance ratio of the reducing component to the oxygen element is equal to or greater than a predetermined threshold value. Here, the "threshold value" in this step is set based on the stoichiometric ratio of the oxide of the reducing component. For example, when carbon element (C) is used as the reducing component, the "oxide of the reducing component" is carbon dioxide (CO2). In this case, in order to suitably reduce at least a part of the valuable metals (Ni, Co) to the state of simple metals (metal Ni, metal Co) in the firing step S24 described later, it is preferable to set the threshold value to a value equal to or greater than the ratio (1 / 2) of the carbon element to the oxygen element in CO2. In the judgment step S22, it is judged whether the amount of substance ratio (hereinafter also referred to as "C / O ratio") of the carbon element (reducing component) to the oxygen element in the recovery target is equal to or greater than 1 / 2. If the C / O ratio is equal to or greater than 1 / 2 (YES in S22 in FIG. 4), proceed to the firing step S24. On the other hand, when the C / O ratio is less than 1 / 2 (NO in S22 in FIG. 4), it is preferable to proceed to the reducing component addition step S23. This makes it possible to more suitably reduce valuable metals to their elemental metal state.

[0035] As described above, the threshold value in the determination step S22 may be set to a value equal to or greater than the stoichiometric ratio of the oxide of the reducing component. For example, when the reducing component is a carbon element, the threshold value may be set to 3 / 4 or more (more preferably 1 or more, even more preferably 5 / 4 or more, and particularly preferably 3 / 2 or more). This allows only the recovery target containing a large amount of the reducing component (carbon element) to be subjected to the calcination step S24. Therefore, the reduction of the valuable metal oxide can be further promoted in the calcination step S24, and most of the valuable metal can be converted into simple metal.

[0036] (c) Reducing component addition step S23 The reducing component adding step S23 is preferably carried out when the result of the determination step S22 is less than the threshold (NO in S22 in FIG. 4). In the reducing component adding step S23, a reducing component is added to the recovery target. For example, it is preferable to add a reducing component (carbon-containing material) to the recovery target determined in the determination step S22 to have a C / O ratio less than 1 / 2 so that the C / O ratio is equal to or greater than the threshold (1 / 2 or more). This makes it possible to more suitably reduce valuable metals to a simple metal state. The carbon-containing material here may be a carbon material such as graphite, hard carbon, or soft carbon. The carbon-containing material may also be a resin material such as polyolefin or polyester. These resin materials are carbonized in the early stage of the baking step S24 to produce carbon elements, and therefore can be used as a source of carbon elements.

[0037] In addition, in the reducing component adding step S23, a reducing component may be added in an amount that greatly exceeds the above-mentioned threshold value. For example, when the reducing component is a carbon element, a carbon-containing material may be added so that the C / O ratio in the recovery target is 3 / 4 or more (more preferably 1 or more, even more preferably 5 / 4 or more, and particularly preferably 3 / 2 or more). This allows the recovery target containing a large amount of reducing component (carbon element) to be subjected to the calcination step S24, thereby further promoting the reduction of valuable metal oxides in the calcination step S24.

[0038] (d) Firing process S24 In the calcination step S24, the recovery target is calcined (heated) at 500°C or higher. This allows at least a portion of the valuable metals (Ni and / or Co) to be reduced to their elemental metal state, and the recovery rate of the valuable metals can be favorably improved. For example, when the recovery target is calcined at 500°C or higher in the calcination step S24, a reaction such as that shown in the following formula (2) may occur. This allows at least a portion of the valuable metals (e.g., Ni, Co) in the recovery target to be reduced to their elemental metal state (metallic Ni, metallic Co).

[0039] LiNi x Co y Mn zO δ +C 1 / 2δ =Li+xNi+yCo+zMn+1 / 2δ·CO2(2)

[0040] The heating temperature in the calcination step S24 (more specifically, the temperature in the heating furnace) may be 500°C or higher. As the heating temperature increases, there is a tendency that the valuable metal is more likely to be generated as an elemental metal. As described above, in the manufacturing method disclosed herein, it is sufficient that at least a part of the valuable metal is reduced to an elemental metal state. In order to more efficiently dissolve the valuable metal in the ammonia leaching step S30 described later, it is preferable that most of the valuable metal is reduced to an elemental metal state. From this viewpoint, the heating temperature is preferably 650°C or higher, may be 700°C or higher, or may be 750°C or higher. On the other hand, from the viewpoint of reducing the valuable metal, the upper limit of the heating temperature is not particularly limited, and may be 1500°C or lower, 1400°C or lower, or 1300°C or lower. In addition, in consideration of reducing the cost required for the calcination step S24, the upper limit of the heating temperature is preferably 1200°C or lower, more preferably 1100°C or lower, and particularly preferably 1000°C or lower. The calcination time in the calcination step S24 is not generally specified because it differs depending on the amount of the material to be recovered, etc. The calcination time in the calcination step S24 is, for example, preferably 1 hour to 12 hours, and more preferably 2 hours to 8 hours.

[0041] Although not particularly limited, the calcination step S24 preferably heats the object to be recovered under an inert atmosphere. This can prevent oxygen element from being supplied to the object to be recovered during heating, and more preferably reduces at least a part of the valuable metal oxide (such as lithium transition metal composite oxide) to a metal element state. Specifically, the calcination step S24 preferably heats the object to be recovered while circulating an inert gas such as argon or nitrogen. Note that the "inert atmosphere" in this specification refers to a heating atmosphere containing the above-mentioned inert gas as a main component. That is, it is not limited to a completely inert atmosphere in which the content of the inert gas is 100% (the content of the oxygen element is 0%), but also includes a heating atmosphere in which the content of the oxygen element is 5% or less (preferably 3% or less, more preferably 1% or less, even more preferably 0.5% or less, and particularly preferably 0.1% or less).

[0042] Although not particularly limited, in the calcination step S24, it is preferable to calcinate the valuable metal so that the elemental metal of the valuable metal is more prevalent than the oxide of the valuable metal. Such a state of the valuable metal can be confirmed, for example, by X-ray diffraction (XRD) analysis. Therefore, in the XRD analysis of the valuable metal, when the ratio of the peak derived from the elemental metal of the valuable metal to the peak derived from the oxide of the valuable metal is 1 or more, it can be said that the elemental metal of the valuable metal is more prevalent than the oxide of the valuable metal. Specifically, for example, in the case of Ni, in the X-ray diffraction using a Mo radiation source, the peak of Ni oxide (NiO) is confirmed at about 19°, and the peak of metallic Ni is confirmed at about 20°. When the ratio of the peak of metallic Ni to the peak of Ni oxide (metallic Ni / Ni oxide) is 1 or more, metallic Ni is more prevalent than Ni oxide.

[0043] (e) Sorting process S25 In the sorting step S25, each component contained in the collected material after firing (heating) is sorted using a sieve. For example, when the collected material is a process waste of a positive electrode plate 30, the positive electrode core 32 may be sorted using a sieve from the process waste and removed from the collected material. When the collected material is an electrode body 20, the negative electrode plate 40 may be removed from the collected material in addition to the positive electrode core 32. When the collected material is a lithium-ion secondary battery 1, the case 10 may be removed from the collected material in addition to the positive electrode core 32 and the negative electrode plate 40. This reduces the content of other metal components (Al, Cu, etc.) in the collected material, which contributes to improving the recovery efficiency of valuable metals (Co, Ni).

[0044] In addition, in the sorting step S25, the objects to be collected may be subjected to a crushing process as necessary. This can improve the efficiency of sorting each component. For example, when the objects to be collected are lithium-ion secondary batteries 1, it is preferable to crush the case 10 and the electrode body 20. This makes it easier to remove the case 10, the positive electrode core 32, and the negative electrode plate 40 from the objects to be collected.

[0045] In addition, the sorting step S25 is not a step intended to completely remove other metal components such as Al from the recovery target. Although details will be described later, even if other metal components remain in the recovery target, valuable metals (Ni and / or Co) can be sufficiently separated from other metal components in the subsequent step (ammonia leaching step S30). In other words, this step can be omitted as necessary. For example, in the case of a recovery target with a low content of other metal components (such as process scraps of positive electrode plates 30), valuable metals can be efficiently recovered even if this step is omitted.

[0046] (3) Ammonia leaching process S30 In the ammonia leaching step S30, the object to be recovered after the heating step S20 is immersed in an aqueous ammonia solution. This makes it possible to obtain a metal solution in which the valuable metals (Ni and / or Co) in the object to be recovered are dissolved in the aqueous ammonia solution. In the manufacturing method disclosed herein, a mixture of ammonia, a pH buffer, and an oxidizing agent is used as the aqueous ammonia solution. In addition to the valuable metal components described above, the object to be recovered after the heating step S20 may contain Li derived from the positive electrode active material, Al derived from the positive electrode core 32 or the case 10, and the like. For example, Al is difficult to dissolve in an aqueous ammonia solution, so it remains as a solid content. Furthermore, in the manufacturing method disclosed herein, the heating step S20 is performed so that at least a part of the valuable metal becomes an elemental metal. As a result, in the ammonia leaching step S30, a higher leaching rate can be achieved in a shorter time than in the past. That is, by performing the ammonia leaching step S30 on the valuable metals at least a part of which has become an elemental metal in the heating step S20, the valuable metals to be recovered (Ni and / or Co) and other metal components (e.g., Al, etc.) can be easily separated. Although not particularly limited, the ammonia leaching step S30 may include a preparation step S31 and a immersion step S32, as shown in Fig. 5. The following will specifically explain the steps.

[0047] (a) Preparation step S31 In the preparation step S31, ammonia, a pH buffer, and an oxidizing agent are mixed to prepare an aqueous ammonia solution. The pH of the aqueous ammonia solution is preferably 8.0 to 11.0, and more preferably 9.0 to 10.0. The concentration of ammonia in the aqueous ammonia solution is preferably 5 wt% to 35 wt%, and more preferably 15 wt% to 30 wt%. This allows valuable metals to be suitably dissolved.

[0048] A pH buffer is a compound that has the function of maintaining the pH of a solution at a predetermined value even if an acid or base is added to a certain extent. In other words, the pH buffer can control the pH of an aqueous ammonia solution to 11 or less. By containing a pH buffer in the aqueous ammonia solution, the pH of the aqueous ammonia solution can be set to the above-mentioned ammonia concentration range without exceeding 11. This allows valuable metals to be suitably dissolved. The pH buffer is not particularly limited as long as it can exhibit pH buffering properties in the aqueous ammonia solution. For example, pH buffers include ammonium salts, amino acids, organic acid salts, borate salts, amine compounds, and the like. The pH buffers can be used alone or in combination of two or more. Among them, ammonium salts are preferred as the pH buffer. Specific examples of ammonium salts include ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium nitrate, and the like. It is more preferred that the pH buffer is ammonium sulfate or ammonium chloride.

[0049] Although not particularly limited, the concentration of the pH buffering agent in the aqueous ammonia solution is preferably 0.5 mol / L or more, may be 1 mol / L or more, or may be 2 mol / L or more. This allows excellent pH buffering properties to be exhibited. Although the upper limit of the concentration of the pH buffering agent is not particularly limited, it may be, for example, 5 mol / L or less, or 4.5 mol / L or less. This allows, for example, the consumption of reagents in the precursor preparation step S40 described later to be reduced.

[0050] An oxidizing agent is a compound that oxidizes other substances. In the manufacturing method disclosed herein, at least a part of the valuable metal is reduced to the state of a simple metal in the heating step S20. Specifically, Co and Ni are present in the recovery target after calcination in a state of divalent or less, more preferably metallic Co and metallic Ni. In order to dissolve such Co and / or Ni in the state of metal ions in the aqueous ammonia solution, it is necessary to increase the valence. For this reason, in the manufacturing method disclosed herein, the aqueous ammonia solution contains an oxidizing agent. The oxidizing agent is not particularly limited as long as it can oxidize valuable metals. For example, the oxidizing agent may be a peroxide, permanganic acid or a salt thereof, nitric acid or a salt thereof, or the like. The oxidizing agent may be used alone or in combination of two or more kinds. Among them, hydrogen peroxide, potassium permanganate, nitric acid, potassium nitrate, sodium peroxide, and manganese oxide may be preferably used as the oxidizing agent.

[0051] Although not particularly limited, the concentration of the oxidizing agent in the aqueous ammonia solution is preferably 0.1 mol / L or more, more preferably 0.5 mol / L or more. This allows the excellent valuable metals to be suitably oxidized. Although not particularly limited, the upper limit of the concentration of the oxidizing agent may be, for example, 3 mol / L or less, or 2 mol / L or less.

[0052] (b) Soaking step S32 In the immersion step S32, the recovery target after the heating step S20 is immersed in the prepared ammonia aqueous solution. As described above, by making at least a portion of the valuable metal into an elemental metal, the solubility in the ammonia aqueous solution is improved. Therefore, in the manufacturing method disclosed herein, a high leaching rate can be achieved even in a shorter time than before. In addition, since Al and the like contained in the recovery target are difficult to dissolve in the ammonia aqueous solution, only the desired valuable metals (here, Ni and Co) can be selectively dissolved in the ammonia aqueous solution.

[0053] The immersion time in the immersion step S32 is preferably 10 minutes or more, more preferably 30 minutes or more, more preferably 60 minutes or more, and particularly preferably 110 minutes or more. This allows Ni and / or Co in the object to be recovered to be sufficiently dissolved in the aqueous ammonia solution. In the manufacturing method disclosed herein, when the immersion time exceeds 120 minutes, almost all of the Ni and / or Co in the object to be recovered can be dissolved in the aqueous ammonia solution. Therefore, in consideration of manufacturing efficiency, the upper limit of the immersion time is preferably 180 minutes or less, and more preferably 150 minutes or less.

[0054] The temperature of the aqueous ammonia solution in the immersion step S32 is not particularly limited. For example, the temperature of the aqueous ammonia solution is preferably 50° C. or higher (more preferably 55° C. or higher, and particularly preferably 60° C. or higher). This allows the ammonia leaching step S30 to be shortened. The upper limit of the temperature of the aqueous ammonia solution is not particularly limited, and may be 90° C. or lower, 85° C. or lower, or 80° C. or lower. Although not particularly limited, the immersion step S32 is preferably performed with stirring.

[0055] As described above, in the manufacturing method disclosed herein, at least a part of the valuable metal is converted into an elemental metal in the heating step S20, so that it can be suitably dissolved in the aqueous ammonia solution. In the conventional method, after the heating step, Co and Ni are recovered as sulfates through an acid leaching step, a neutralization step, a washing step, and a solvent extraction step. On the other hand, according to the manufacturing method disclosed herein, Co, Ni and other metal components can be separated by only carrying out the ammonia leaching step S30 after the heating step S20. In the manufacturing method disclosed herein, since the acid leaching step is not carried out, there is no need to carry out the neutralization step. In addition, since the separated Ni and Co are present in the aqueous ammonia solution, the solution can be used as it is to carry out the step of preparing a cathode active material precursor (precursor preparation step S40) described later. In other words, according to the manufacturing method disclosed herein, while achieving a high leaching rate of valuable metals, the number of steps from the completion of the heating step S20 to the precursor preparation step S40 can be significantly reduced.

[0056] (4) Precursor preparation process S40 In the precursor preparation step S40, a positive electrode active material precursor (metal composite hydroxide) is precipitated using the metal solution obtained in the ammonia leaching step S30. In general, the step of preparing a positive electrode active material precursor is performed by dropping an alkaline solution (particularly ammonia water) into a solution of a metal sulfate, and stirring the solution while controlling the pH, thereby coprecipitating and crystallizing particles of a metal composite hydroxide in a reaction tank. The metal solution after the ammonia leaching step S30 contains Ni and / or Co in the form of an ammine complex in the aqueous ammonia solution. Therefore, the metal solution obtained in the ammonia leaching step S30 can be used as it is in the precursor preparation step S40. By stirring the metal solution while adjusting the pH, a positive electrode active material precursor (metal composite hydroxide) can be crystallized.

[0057] In the precursor preparation step S40, the pH of the metal solution can be controlled to about 9 to 13. In the precursor preparation step S40, the metal solution can be stirred while adding an alkaline solution (e.g., sodium hydroxide or sodium carbonate) as necessary to control the pH. The amounts of Ni and Co in the metal solution obtained in the ammonia leaching step S30 can be determined by ICP analysis. For this reason, Ni, Co, or other metal components such as Mn may be added depending on the composition of the target positive electrode active material. Such metal components can be added in the form of metal sulfates, hydrates, etc.

[0058] (5) Active material generation process S50 In the active material generating step S50, the positive electrode active material precursor (metal composite hydroxide) obtained in the precursor producing step S40 and a Li compound (e.g. Li carbonate) are used to generate a battery material (positive electrode active material). For example, the positive electrode active material precursor and the Li compound prepared above are mixed, and the mixture is fired. This allows the positive electrode active material (lithium transition metal composite oxide) of a lithium ion secondary battery to be manufactured.

[0059] The manufacturing method of the battery material according to the present embodiment has been described above. As described above, in the manufacturing method according to the present embodiment, the heating step S20 is performed by heating the recovery target at 500° C. or higher so that a part of the valuable metal contained in the recovery target is converted into an elemental metal. This allows the valuable metal (Ni and / or Co) to be suitably dissolved in the ammonia aqueous solution in the ammonia leaching step S30. Therefore, even if the leaching step time is short, the recovery rate of the valuable metal can be improved. In addition, in the manufacturing method disclosed herein, since the acid leaching step is not performed as in the conventional method, the precursor of the positive electrode active material can be produced without performing the neutralization step or the solvent step. According to this manufacturing method, the recovery rate of the valuable metal is improved while the manufacturing process is significantly shortened.

[0060] 3. Other embodiments An embodiment of the technology disclosed herein has been described above. Note that the technology disclosed herein is not limited to the above embodiment, and includes other embodiments in which various configurations are modified. Other examples of the embodiment of the technology disclosed herein will be described below.

[0061] In the manufacturing method according to the above embodiment, Ni and / or Co are recovered as valuable metals. However, in the manufacturing method disclosed herein, lithium (Li) can be recovered (produced) in addition to the above nickel (Ni) and cobalt (Co) as needed. That is, the description of the above embodiment is not intended to limit each step. In the manufacturing method disclosed herein, each step may be appropriately added, deleted, or changed as needed.

[0062] The following is an example of a means for recovering Li. First, when the heating step S20 is performed, a chlorination roasting step is performed in which a non-metallic chlorine compound (such as HCl) is added to the object to be recovered and roasted. As a result, Li in the object to be recovered reacts with the non-metallic chlorine compound to generate LiCl. Next, a water leaching step is performed in which the object to be recovered after roasting is immersed in water. Since the above LiCl is a water-soluble compound, Li can be recovered by simply bringing the object to be recovered into contact with water.

[0063] In addition, the detailed conditions in the heating step S20 may be changed as appropriate. For example, in the manufacturing method according to the above embodiment, carbon element is used as the reducing component. However, as described above, the reducing component is not particularly limited as long as it is a component that can reduce Ni and Co in the firing step S24. Examples of reducing components other than carbon element (C) include metallic reducing components such as lithium (Li), cesium (Cs), potassium (K), barium (Ba), strontium (Sr), calcium (Ca), sodium (Na), magnesium (Mg), aluminum (Al), titanium (Ti), zirconium (Zr), and manganese (Mn). It is preferable that these metallic reducing components are present in the recovery target in the form of sulfite or the like. For example, when calcium sulfite (CaSO3) is used as the reducing component, at least a part of the valuable metal is reduced to a metal element in the heating step S20, and calcium oxide (CaO) is generated. In this case, the threshold value in the determination step S22 is set to a value equal to or greater than the stoichiometric ratio (1 / 1) of CaO. This allows the valuable metals in the object to be recovered to be appropriately reduced to the state of elemental metal. In the measurement step S21, the means for measuring the metal-based reducing components include ICP, SEM-EDS analysis, and XRF analysis. The reducing components to be determined in the determination step S22 and the reducing components to be added in the reducing component addition step S23 may be the same or different. For example, when it is determined in the determination step S22 that the carbon element (C) is insufficient, calcium sulfite (CaSO3) may be added in the reducing component addition step S23. Even in this case, the valuable metals can be appropriately reduced to the state of elemental metal in the firing step S24.

[0064] [Test example] Test examples relating to the technology disclosed herein will be described below. Note that the contents of the test examples described below are not intended to limit the technology disclosed herein.

[0065] 1. Sample preparation (Example 1) In this test, positive electrode plates were collected, and test samples were prepared for the collected objects in the following manner. First, positive electrode plates to be collected were prepared. The positive electrode plates used had a positive electrode core (Al foil) with a positive electrode active material layer applied to its surface. The positive electrode active material used in this test was lithium nickel cobalt manganese composite oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Then, the positive electrode plate was crushed and sieved through a sieve with 500 μm openings to prepare a powder.

[0066] Next, a part of the prepared powder was taken and dissolved in sulfuric acid. Then, ICP was performed on the solution to measure the total amount of Ni, Co, and Mn, M. The composition of the positive electrode active material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Based on the above, the amount of substance N of the oxygen element was set to twice the total amount of substance M (N=2M) based on the above. In this test, a thermogravimetric differential thermal analysis (TG-DTA) was performed on a part of the prepared powder. In this thermogravimetric differential thermal analysis, the powder was heated in an air atmosphere at 800°C. In this analysis, the heating rate from room temperature (20°C) to 800°C was set to 5°C / min. The carbon amount in the prepared powder was measured. Then, graphite was added to the powder so that the measured amount of substance ratio (C / O ratio) of oxygen element to carbon element was equal to or greater than the stoichiometric ratio of CO2 (1 / 2), to prepare a test sample of Example 1.

[0067] Next, the test sample was heated under an inert atmosphere. Specifically, in Example 1, the test sample was placed in an electric furnace, and the temperature inside the furnace was raised to 150°C while supplying Ar gas. The temperature rise rate was set to 5°C / min. Then, heating was performed for 5 hours while maintaining the temperature inside the furnace at 150°C. After that, the temperature inside the furnace was cooled to 50°C, and the sample of Example 1 was collected.

[0068] The collected sample was then subjected to ammonia leaching. Specifically, an aqueous ammonia solution was prepared by mixing 28 wt% ammonia (NH3), 2 mol / L ammonium sulfate ((NH4)2SO4) as a pH buffer, and 0.5 mol / L hydrogen peroxide (H2O2) as an oxidizing agent. The heated sample was then placed in the aqueous ammonia solution. The temperature of the aqueous ammonia solution was maintained at 80°C, and the stirring process was continued for 2 hours at a stirring speed of 500 rpm.

[0069] (Examples 2 to 7) In Examples 2 to 7, the temperature inside the furnace was changed as shown in Table 1. Other than this, samples of Examples 2 to 7 were obtained in the same manner as in Example 1. Then, ammonia leaching was performed on the samples of Examples 2 to 7.

[0070] (Examples 8 and 9) In Examples 8 and 9, the furnace temperature was changed as shown in Table 1. Other than this, samples of Examples 8 and 9 were obtained in the same manner as in Example 1. Then, ammonia leaching was performed on the samples of Examples 8 and 9 by changing the concentration of the pH buffer agent as shown in Table 1.

[0071] (Example 10) In Example 10, no graphite was added. The temperature inside the furnace was changed as shown in Table 1. Other than this, the sample of Example 10 was obtained in the same manner as in Example 1. Then, the sample of Example 10 was subjected to ammonia leaching.

[0072] 2.Evaluation Test (1)XRD analysis X-ray diffraction (XRD) analysis using a Mo radiation source was performed on the test samples of each example after heating to evaluate the state of the Ni element in the test sample. The results are shown in Table 1. The XRD chart of Example 5 is shown in FIG. 6. As shown in FIG. 6, when no peak originating from the positive electrode active material was confirmed near 8° and peaks were confirmed near 19° and 20°, the Ni element after firing was evaluated as being at least partially in the form of a metal element ("oxide + metal element" in Table 1). When no peak originating from the positive electrode active material was confirmed near 8° and a peak was confirmed only near 20°, the Ni element after firing was evaluated as being mostly in the form of a metal element ("metal element" in Table 1). When a peak originating from the positive electrode active material was confirmed near 8° or a peak was confirmed only near 19°, the Ni element was evaluated as being present entirely in the form of an oxide ("oxide" in Table 1).

[0073] In addition, the state of the Co element in the test sample was also analyzed by XRD according to the same procedure as for the evaluation of the state of Ni above. The results are shown in Table 1.

[0074] Furthermore, in this test, in Examples 3 to 10 in which no peak derived from the positive electrode active material was observed around 8°, the peak intensity ratio of the metal Ni peak to the Ni oxide peak (metal Ni / Ni oxide) was calculated. The results are shown in Table 1. When the peak intensity ratio (metal Ni / Ni oxide) was less than 1, it was evaluated that a Ni oxide-dominant sample had been produced, and when the peak intensity ratio was 1 or more, it was evaluated that a metal Ni-dominant sample had been produced.

[0075] (2) Leaching rate of ammonia leaching ICP analysis was performed on the test samples of each example after ammonia leaching, and the leaching rates of Ni and Co for each example were calculated. Specifically, first, the metal solution in which the sample of each example was dissolved was filtered. Next, ICP was performed on the filtrate to measure the amounts of Ni and Co contained in the filtrate. Then, the leaching rates of each metal element were calculated based on the following formula (3). Note that the "amount of substance before ammonia leaching" in formula (3) is a value calculated by measuring and grasping the amount of substance per 1g by ICP analysis and multiplying it by the weight of the sample added to ammonia. Leaching rate = (amount of substance in filtrate solution / amount of substance before ammonia leaching) x 100 (3)

[0076] [Table 1]

[0077] As shown in Table 1, in Examples 3 to 10 in which the firing temperature was 500° C. or higher, at least a part of Ni was in the form of an elemental metal, and at least a part of Co was in the form of an elemental metal. It is also found that ammonia leaching achieved a Ni leaching rate of 71% or higher and a Co leaching rate of 67% or higher. That is, by heating the recovery target at 500° C. or higher so as to reduce at least a part of the valuable metal to an elemental metal state, and immersing the heated recovery target in an aqueous ammonia solution containing ammonia, a pH buffer, and an oxidizing agent, a high leaching rate of valuable metals and a highly efficient manufacturing method for battery materials can be realized.

[0078] Although the technology disclosed herein has been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. In other words, the technology disclosed herein includes the embodiments described in the following items 1 to 8.

[0079] <Item 1> A preparation step of preparing a recovery target containing at least one of Ni and Co as a valuable metal; A heating step of heating the recovery target at 500° C. or higher so as to reduce at least a portion of the valuable metals to a metal elemental state; an ammonia leaching process in which the recovery target after the heating process is immersed in an aqueous ammonia solution containing ammonia, a pH buffer, and an oxidizing agent to obtain a metal solution containing the valuable metal; A method for producing a battery material comprising the steps of: <Item 2> 2. The method for producing a battery material according to item 1, wherein the concentration of the pH buffer is 0.5 mol / L or more. <Item 3> 3. The method for producing a battery material according to claim 1, wherein the heating step includes a reducing component adding step of adding a reducing component such that an amount of substance of the reducing component relative to an amount of substance of elemental oxygen contained in the target to be recovered is equal to or greater than a threshold based on a stoichiometric ratio of an oxide of the reducing component. <Item 4> 4. The method for producing a battery material according to item 3, wherein the reducing component is a carbon element, and the threshold value is a value equal to or greater than the stoichiometric ratio of CO2. <Item 5> 5. The method for producing a battery material according to any one of items 1 to 4, wherein the heating step heats the recovery target at 650°C to 1000°C. <Item 6> 6. The method for producing a battery material according to any one of items 1 to 5, wherein the heating step is performed such that in an XRD analysis of the valuable metal, a ratio of a peak originating from an elemental metal of the valuable metal to a peak originating from an oxide of the valuable metal is 1 or more. <Item 7> 7. The method for producing a battery material according to any one of items 1 to 6, further comprising the step of producing a positive electrode active material precursor by using the metal solution in the ammonia leaching step. <Item 8> 8. The method for producing a battery material according to any one of items 1 to 7, wherein the target to be recovered includes at least one selected from the group consisting of a lithium nickel composite oxide, a lithium cobalt composite oxide, a lithium nickel manganese composite oxide, a lithium manganese cobalt composite oxide, a lithium nickel cobalt composite oxide, and a lithium nickel manganese cobalt composite oxide. [Explanation of symbols]

[0080] 1. Lithium-ion secondary battery 10 Cases 12 Positive terminal 14 Negative terminal 20 Electrode body 30 Positive plate 32 Positive electrode core 34 Cathode active material layer 40 Negative plate 42 Negative electrode core 44 Negative electrode active material layer 50 Separator

Claims

1. A preparation step of preparing a recovery target containing at least one of Ni and Co as a valuable metal; A heating step of heating the recovery target at 500° C. or higher so as to reduce at least a portion of the valuable metal to a metal elemental state; an ammonia leaching process in which the recovery target after the heating process is immersed in an aqueous ammonia solution containing ammonia, a pH buffer, and an oxidizing agent to obtain a metal solution containing the valuable metal; A method for producing a battery material comprising the steps of:

2. The method for producing a battery material according to claim 1 , wherein the concentration of the pH buffer is 0.5 mol / L or more.

3. 2. The method for producing a battery material according to claim 1, wherein the heating step includes a reducing component adding step of adding the reducing component so that an amount of the reducing component relative to an amount of the oxygen element contained in the recovery target is equal to or greater than a threshold based on a stoichiometric ratio of an oxide of the reducing component.

4. The reducing component is carbon element, and the threshold value is CO ２ The method for producing a battery material according to claim 3, wherein the value is equal to or greater than the stoichiometric ratio of

5. The method for producing a battery material according to claim 1 , wherein the heating step heats the recovery target at 650° C. to 1000° C.

6. 2. The method for producing a battery material according to claim 1, wherein the heating step is performed so that in an XRD analysis of the valuable metal, a ratio of a peak due to an elemental metal of the valuable metal to a peak due to an oxide of the valuable metal is 1 or more.

7. The method for producing a battery material according to claim 1 , further comprising the step of producing a positive electrode active material precursor using the metal solution in the ammonia leaching step.

8. 2. The method for producing a battery material according to claim 1, wherein the target to be recovered includes at least one selected from the group consisting of a lithium nickel composite oxide, a lithium cobalt composite oxide, a lithium nickel manganese composite oxide, a lithium manganese cobalt composite oxide, a lithium nickel cobalt composite oxide, and a lithium nickel manganese cobalt composite oxide.

Images