Method for producing a precursor of a positive electrode active material

Abstract

This invention provides a method for producing a precursor of a positive electrode active material that can reduce the generation of waste. [Solution] The present disclosure provides a method for producing a precursor of a positive electrode active material, comprising the steps of: contacting a raw material containing Ni and Co with an aqueous phase containing ammonia and ammonium sulfate to leach Ni and Co into the aqueous phase; recovering and removing ammonia from the aqueous phase; dissolving a manganese salt in the aqueous phase from which ammonia has been removed; and crystallizing the aqueous phase from which the manganese salt has been dissolved using ammonium bicarbonate to obtain a carbonate containing Ni, Co, and Mn.

Description

Technical Field

[0001] The present disclosure relates to a method for producing a precursor of a positive electrode active material.

Background Art

[0002] Lithium-ion secondary batteries are widely used in various fields as power sources for vehicle driving, portable power sources, etc. In recent years, from the perspective of SDGs, the material recycling of used lithium-ion secondary batteries has been promoted. Regarding material recycling, technologies have been developed to separate metal elements contained in the positive electrode active material from used lithium-ion secondary batteries and reuse them in the production of positive electrode active materials.

[0003] In the production of the positive electrode active material of a lithium-ion secondary battery, typically, a hydroxide containing metal elements other than Li (for example, in the case of lithium nickel cobalt manganese composite oxide, Ni, Co, and Mn) is first prepared as a precursor by a crystallization method (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the prior art, as described in Patent Document 1, in the production of the precursor, sulfates are often used as metal element sources other than Li. Also, in the production of the precursor, sodium hydroxide is generally used for pH adjustment. As a result, in the prior art, there is a problem that sodium sulfate, which becomes waste in the production of the precursor, is by-produced.

[0006] Therefore, this disclosure aims to provide a method for producing a precursor of a positive electrode active material that can reduce the generation of waste. [Means for solving the problem]

[0007] The present disclosure provides a method for producing a precursor of a positive electrode active material, comprising the steps of: contacting a raw material containing Ni and Co with an aqueous phase containing ammonia and ammonium sulfate to leach Ni and Co into the aqueous phase; recovering and removing ammonia from the aqueous phase; dissolving a manganese salt in the aqueous phase from which ammonia has been removed; and crystallizing the aqueous phase from which the manganese salt is dissolved using ammonium bicarbonate to obtain a carbonate containing Ni, Co, and Mn.

[0008] This configuration allows for the production of a precursor for the cathode active material while reducing waste generation. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a flowchart showing the steps for the method of producing the cathode active material precursor of this disclosure. [Figure 2] Figure 2 is a schematic diagram of the operations and reagents used in the method for producing the cathode active material precursor of this disclosure. [Modes for carrying out the invention]

[0010] Embodiments relating to this disclosure will be described below with reference to the drawings. Matters not mentioned herein but necessary for the implementation of this disclosure can be understood as design matters for those skilled in the art based on the prior art. This disclosure can be implemented based on the contents disclosed herein and common technical knowledge in the art. The numerical range expressed as "A to B" in this specification includes A and B.

[0011] In this specification, "secondary battery" refers to an energy storage device that can be repeatedly charged and discharged. Furthermore, in this specification, "lithium-ion secondary battery" refers to a secondary battery that uses lithium ions as a charge carrier and achieves charging and discharging through the transfer of charge associated with lithium ions between the positive and negative electrodes.

[0012] Figure 1 shows the essential and optional steps of the method for producing the precursor of the positive electrode active material of this disclosure. The method for producing the precursor of the positive electrode active material of this disclosure comprises, as essential steps, a step of contacting a raw material containing Ni and Co with an aqueous phase containing ammonia and ammonium sulfate to leach Ni and Co into the aqueous phase (hereinafter also referred to as the "leaching step") S101; a step of recovering and removing ammonia from the aqueous phase (hereinafter also referred to as the "ammonia removal step") S102; a step of dissolving a manganese salt in the aqueous phase from which ammonia has been removed (hereinafter also referred to as the "Mn salt dissolution step") S103; and a step of crystallizing the aqueous phase in which the manganese salt has been dissolved using ammonium bicarbonate to obtain a carbonate containing Ni, Co, and Mn (hereinafter also referred to as the "crystallization step") S104. The method for producing the cathode active material precursor of this disclosure may further include, as an optional step, a step S105 in which the carbonate containing Ni, Co, and Mn is heat-treated to obtain an oxide containing Ni, Co, and Mn (hereinafter also referred to as the "heat treatment step"). Figure 2 shows an overview of the operations performed and the reagents used in the method for producing the cathode active material precursor of this disclosure. Each step will be described in detail below.

[0013] <Leaching process S101> The types of raw materials containing Ni and Co are not particularly limited, as long as they contain Ni and Co. The raw materials containing Ni and Co may be one compound containing Ni and Co, or a mixture of two or more compounds.

[0014] If the raw materials are a mixture, for example, the mixture may contain at least a compound containing Ni and a compound containing Co. For example, the mixture may contain at least a compound containing Ni and Co, and a compound containing either Ni or Co. The mixture may also further contain compounds that do not contain Ni or Co.

[0015] Examples of raw materials containing Ni and Co include ores containing Ni and Co (especially oxide ores), inorganic compounds containing Ni and Co (especially inorganic oxides), and battery waste containing Ni and Co. From the perspective of material recycling, it is advantageous to use battery waste containing Ni and Co as a raw material.

[0016] Specific examples of battery waste include black mass from used lithium-ion secondary batteries (especially black mass obtained by crushing and roasting used lithium-ion secondary batteries), positive electrode waste extracted from used lithium-ion secondary batteries, electrode body waste extracted from used lithium-ion secondary batteries, positive electrode waste deemed to be defective, electrode body waste deemed to be defective, and positive electrode active material deemed to be defective. In these battery wastes, if lithium nickel cobalt manganese composite oxide or lithium nickel cobalt aluminum composite oxide is used as the positive electrode active material, the battery waste will contain Ni and Co.

[0017] It is more preferable that the raw materials contain Ni and Co as metals. From this viewpoint, if the raw materials are waste, it is preferable that they have been reductively roasted. Preferably, the waste is black mass obtained by crushing and roasting used lithium-ion secondary batteries.

[0018] The black mass can be obtained, for example, by crushing a lithium-ion secondary battery according to a known method, performing sieving if necessary, and roasting in an atmosphere at 400°C to 1500°C (preferably 700°C to 1000°C) with an oxygen concentration of 5% by volume or less (preferably 1% by volume or less) (particularly, an inert gas atmosphere such as argon gas or nitrogen gas) for 1 hour to 24 hours (preferably 4 hours to 12 hours).

[0019] The raw material may further contain elements other than Ni and Co. For example, the raw material may further contain Mn. When the raw material is battery waste, Mn may be derived from a lithium nickel cobalt manganese composite oxide which is a positive electrode active material. For example, the raw material may further contain Li. When the raw material is battery waste, Li may be derived from a positive electrode active material, a supporting salt, etc. The raw material may further contain Al. When the raw material is battery waste, Al may be derived from a lithium nickel cobalt aluminum composite oxide which is a positive electrode active material, a positive electrode current collector, an electrode terminal, a battery case, etc. The raw material may further contain Cu. When the raw material is battery waste, Cu may be derived from a negative electrode current collector, an electrode terminal, etc. When the raw material is battery waste, it is preferably free from at least one of Cu and Li, and more preferably free from both Cu and Li. Therefore, the battery waste may have been subjected to some treatment, for example, a treatment for removing at least one of Cu and Li may have been performed.

[0020] In the leaching step S101, an aqueous phase (i.e., an aqueous solution) containing ammonia and ammonium sulfate is used as the leaching agent. By performing leaching using such an aqueous phase, Ni and Co can be leached from the raw material containing Ni and Co into the aqueous phase.

[0021] The concentration of ammonia in the aqueous phase is not particularly limited, but a higher concentration results in higher leaching ability. Therefore, the concentration of ammonia in the aqueous phase is, for example, 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. Also, the upper limit of the ammonia concentration is the saturation concentration of ammonia in water, and thus is about 35% by mass. From the viewpoints of leaching ability and ease of handling, a concentration of ammonia of 15% by mass to 25% by mass is particularly preferred.

[0022] Ammonium sulfate acts as a pH adjuster. The amount of ammonium sulfate in the aqueous phase is such that the pH of the ammonia leachate is, for example, 9 to 12, preferably 10 to 11 at 20°C. The concentration of ammonium sulfate in the aqueous phase is preferably 0.5 mol / L or more, more preferably 1 mol / L or more, and even more preferably 2 mol / L or more. On the other hand, the concentration of ammonium sulfate in the aqueous phase may be 3 mol / L or less, or 2.5 mol / L or less.

[0023] The aqueous phase may contain only water, ammonia, and ammonium sulfate. The aqueous phase may further contain components other than water, ammonia, and ammonium sulfate within a range that does not inhibit the effects of the present disclosure (for example, at a concentration of less than 10% by mass, 5% by mass or less, or 1% by mass or less).

[0024] The amount of the aqueous phase used is not particularly limited and may be of the same degree as the amount of the aqueous phase used in known ammonia leaching methods. For example, the amount of the aqueous phase used is such that the raw material containing Ni and Co is completely immersed.

[0025] The leaching step S101 can be carried out, for example, as follows. First, prepare a container. The container may be a known container used for ammonia leaching. If necessary, attach heating means such as a heater, temperature measuring means such as a thermometer and a temperature sensor, and stirring means such as a stirring blade and a magnetic stirrer to the container.

[0026] The raw materials and aqueous phase are placed in the container. The order in which they are placed is not particularly limited; they can be placed in any order or simultaneously. This allows the raw materials and aqueous phase to come into contact, enabling ammonia leaching.

[0027] The leaching temperature in the leaching process S101 is not particularly limited and may be room temperature (i.e., 1°C to 30°C). Leaching may also be performed under heating. From the viewpoint of a high leaching rate, the leaching temperature is preferably 50°C or higher, more preferably 55°C or higher, even more preferably 60°C or higher, and particularly preferably 80°C or higher. The leaching temperature may also be below the boiling point of water, and may be 90°C or lower, 85°C or lower, or 80°C or lower.

[0028] Stirring is preferable during leaching. The stirring speed is not particularly limited, but is preferably 200 rpm or higher, more preferably 300 rpm or higher, and even more preferably 400 rpm or higher. The stirring speed may be 2000 rpm or lower, 1000 rpm or lower, or 800 rpm or lower.

[0029] The leaching time is not particularly limited and can be appropriately determined according to the leaching temperature, stirring speed, etc. The leaching time is, for example, 1 hour or more, preferably 2 hours or more, and more preferably 3 hours or more. From the viewpoint of work efficiency, the leaching time is, for example, 48 hours or less, preferably 24 hours or less, more preferably 12 hours or less, and even more preferably 6 hours or less.

[0030] Leaching can be terminated by solid-liquid separation, such as by performing a filtrate. In this way, Ni and Co can be leached into the aqueous phase, thereby obtaining an aqueous phase containing Ni and Co. On the other hand, a solid residue can be obtained. If the raw materials contain metal elements other than Ni and Co, the solid residue may also contain metal elements other than Ni and Co.

[0031] The leaching operation for Ni and Co may be performed only once or multiple times. Performing the leaching operation multiple times allows for the recovery of more Ni and Co. When performing the leaching operation multiple times, the solid residue obtained by solid-liquid separation after leaching should be leached using an aqueous phase containing ammonia and ammonium sulfate. This aqueous phase may be fresh or may have been used for leaching once before.

[0032] [Ammonia removal process S102] The ammonia removal step S102 removes ammonia from the aqueous phase containing Ni and Co obtained in the leaching step S101. At this time, the removed ammonia is recovered.

[0033] The ammonia removal step S102 can be carried out in accordance with known methods. Specifically, for example, it can be carried out as follows: Prepare an open container (i.e., a container that is not sealed and is open to the atmosphere). The open container may be one of known types. Attach heating means such as a heater, temperature measuring means such as a thermometer or temperature sensor, stirring means such as a stirring blade or magnetic stirring bar to the open container.

[0034] On the other hand, an ammonia collection device is prepared. Known devices can be used as ammonia collection devices. For example, an ammonia collection device comprises a suction hood and an ammonia collection unit. The suction hood is installed, for example, above an open container. The ammonia collection unit cools the aspirated ammonia gas and recovers it as ammonia water. Alternatively, for example, the ammonia collection unit contains an ammonia collection liquid (for example, an acidic aqueous solution with a pH of less than 7, especially a sulfuric acid solution with a pH of less than 7), and is configured so that the gas aspirated from the suction hood can pass through the ammonia collection liquid. The ammonia collection device may also have an ammonia separation unit and an ammonia recovery unit. The ammonia separation unit is configured to separate ammonia from the collection liquid by distillation, adsorption with an adsorbent, membrane separation, etc. The ammonia recovery unit is a tank, etc., connected to the ammonia separation unit by piping, etc., and is configured to recover the ammonia separated in the ammonia separation unit. Note that the configuration of the ammonia collection device is not limited to the above.

[0035] The aqueous phase that has undergone the leaching process S101 is added to an open container, and the aqueous phase is heated. This allows ammonia to volatilize from the aqueous phase. The heating temperature is not particularly limited as long as the ammonia volatilizes, but it is preferably 50°C or higher, more preferably 70°C or higher, and even more preferably 90°C or higher. On the other hand, the heating temperature may be below the boiling point of water (i.e., 100°C).

[0036] The heating time can be appropriately determined according to the heating temperature. The higher the heating temperature, the shorter the heating time can be. The heating time is, for example, 1 hour or more, preferably 3 hours or more, more preferably 6 hours or more, and even more preferably 9 hours or more. The heating time is preferably 72 hours or less, more preferably 48 hours or less, and even more preferably 24 hours or less.

[0037] Stirring may be performed during heating. The stirring speed is not particularly limited, but is preferably 200 rpm or more, more preferably 400 rpm or more, and still more preferably 600 rpm or more. The stirring speed may be 2000 rpm or less, 1000 rpm or less, or 800 rpm or less.

[0038] Ammonia volatilized by heating is recovered by an ammonia collection device. Specifically, for example, ammonia volatilized from a suction hood is suctioned, and the ammonia is captured by the capture liquid in the ammonia collection section. In this way, the ammonia removal step S102 can be carried out. As shown in FIG. 2, the ammonia recovered in the ammonia removal step S102 can be reused in the aqueous phase used in the leaching step S101. Therefore, from the viewpoint of further reducing waste, in the manufacturing method of the present disclosure, it is preferable to reuse the ammonia recovered in the ammonia removal step S102 in the leaching step S101. Alternatively, the ammonia recovered in the ammonia removal step S102 can be converted to ammonium hydrogen carbonate and reused in the crystallization step S104 described later. The conversion of ammonia to ammonium hydrogen carbonate can be carried out according to a known method.

[0039] Note that the greater the amount of ammonia volatilized, the lower the pH of the aqueous phase and the higher the precipitation rate of the carbonate in the crystallization step S104. Therefore, the ammonia removal step S102 is preferably carried out until the pH of the aqueous phase becomes 9.0 or less, more preferably until it becomes less than 8.0, still more preferably until it becomes less than 7.5, and particularly preferably until it becomes less than 7.0.

[0040] In the Mn salt dissolution step S103, a manganese salt is dissolved in the aqueous phase from which ammonia has been removed in the ammonia removal step S102.

[0041] Since manganese salts dissolve in the aqueous phase, the manganese salt used must be water-soluble. Examples of such manganese salts include manganese sulfate, manganese nitrate, and manganese chloride, with manganese sulfate being particularly preferred. When manganese sulfate is used as the manganese salt, sulfate ions are contained in the resulting aqueous phase. These sulfate ions can be recovered in the form of ammonium sulfate after the crystallization step S104. This ammonium sulfate can be reused in the leaching step S101. Therefore, when manganese sulfate is used as the manganese salt, no waste can be generated in the method for producing the cathode active material precursor of this disclosure.

[0042] Furthermore, if the raw materials containing Ni and Co also contain Mn, the solid residue obtained in the leaching step S101 will also contain Mn. This Mn contained in the solid residue can be recovered and recycled as manganese salt. Therefore, if the raw materials containing Ni and Co also contain Mn, and the manganese salt used in the Mn salt dissolution step S103 is made from recycled Mn contained in the solid residue obtained in the leaching step S101, it is advantageous from the viewpoint of resource recycling. For this reason, it is preferable that the Mn in the manganese salt is Mn recovered from the solid residue generated in the leaching step S101.

[0043] The amount of manganese salt added may be appropriately selected depending on the molar ratio of Ni, Co, and Mn in the desired positive electrode active material. That is, the amount of manganese salt added may be such that the molar ratio of Ni, Co, and Mn in the aqueous phase matches the molar ratio of Ni, Co, and Mn in the desired positive electrode active material.

[0044] The manganese salt may be added to the aqueous phase in solid form. Alternatively, the manganese salt may be dissolved in water, and the resulting aqueous solution of the manganese salt may be added to the aqueous phase. When dissolving the manganese salt in the aqueous phase, heating, stirring, etc., may be performed.

[0045] As described above, the Mn salt dissolution step S103 can be carried out, and an aqueous phase containing Ni, Co, and Mn can be obtained.

[0046] <Crystallization process S104> In crystallization step S104, crystallization is carried out using ammonium bicarbonate. Specifically, ammonium bicarbonate is added to the aqueous phase to carry out a crystallization reaction, precipitating carbonates containing Ni, Co, and Mn.

[0047] Ammonium bicarbonate functions as an ammonium feeder for crystallization reactions, a pH adjuster in crystallization reactions, and a carbon dioxide source for carbonates. Adding ammonium bicarbonate to the aqueous phase triggers a crystallization reaction, resulting in the precipitation of carbonates containing Ni, Co, and Mn. Because the crystallization reaction is easily controlled, it is preferable to add ammonium bicarbonate dropwise to the aqueous phase in the form of an aqueous solution.

[0048] The amount of ammonium bicarbonate added is preferably 1.5 times or more, more preferably 2.0 times or more, and even more preferably 2.5 times or more, relative to the total number of moles of Ni, Co, and Mn contained in the aqueous phase. The amount of ammonium bicarbonate added may be 10 times or less, 5 times or less, or 3 times or less, relative to the total number of moles of Ni, Co, and Mn contained in the aqueous phase.

[0049] Crystallization may be carried out at room temperature (i.e., 1°C to 30°C) or under heating. When heating is used, the heating temperature is preferably below the decomposition temperature of the resulting carbonate. Specifically, the heating temperature is preferably 70°C or lower (particularly 40°C to 70°C). From the viewpoint of energy saving, crystallization is preferably carried out at room temperature (i.e., 1°C to 30°C).

[0050] Stirring is preferable during crystallization. The stirring speed is not particularly limited, but is preferably 200 rpm or higher, more preferably 400 rpm or higher, and even more preferably 600 rpm or higher. The stirring speed may be 2000 rpm or lower, 1000 rpm or lower, or 800 rpm or lower.

[0051] The crystallization time is not particularly limited and can be appropriately determined according to the leaching temperature, stirring speed, etc. The crystallization time is, for example, 10 minutes or more, preferably 1 hour or more, and more preferably 2 hours or more. From the viewpoint of operational efficiency, the crystallization time is, for example, 48 hours or less, preferably 24 hours or less, more preferably 12 hours or less, and even more preferably 6 hours or less.

[0052] Crystallization can precipitate carbonates containing Ni, Co, and Mn. The precipitated carbonates containing Ni, Co, and Mn can be recovered according to known methods. For example, the precipitated carbonates containing Ni, Co, and Mn can be separated from the aqueous phase by solid-liquid separation such as filtration, washed with water, and then dried to recover the carbonates containing Ni, Co, and Mn.

[0053] On the other hand, the aqueous phase separated from the carbonate contains ammonia and ammonium sulfate, derived from the ammonia and ammonium sulfate used in the leaching step S101 and the ammonium bicarbonate used in the crystallization step S104. This ammonia and ammonium sulfate can be reused in the leaching step S101 (see Figure 2). In particular, the aqueous phase separated from the carbonate may contain residual Ni, residual Co, and carbonate ions, but these components do not adversely affect the execution of the leaching step S101. Therefore, the aqueous phase separated from the carbonate after the crystallization step S104 can be used directly in the leaching step S101. Alternatively, the ammonia and ammonium sulfate may be separated from the aqueous phase before reuse.

[0054] Therefore, it is preferable to reuse the ammonia and ammonium sulfate contained in the aqueous phase after the crystallization step S104 in the leaching step S101.

[0055] Thus, in the method for producing the cathode active material precursor of this disclosure, ammonia and ammonium sulfate are by-products in crystallization, and these can be reused in the leaching step S101, making it possible to significantly reduce waste, and even eliminate waste. Therefore, the method for producing the cathode active material precursor of this disclosure is excellent in terms of resource recycling. Furthermore, since black mass derived from used lithium-ion secondary batteries can be used as a raw material, it is extremely useful in material recycling.

[0056] Besides hydroxides, carbonates are also known as precursors for positive electrode active materials. By performing the crystallization step S104, carbonates containing Ni, Co, and Mn, which are precursors for positive electrode active materials, can be obtained. Therefore, carbonates containing Ni, Co, and Mn can be used in the production of positive electrode active materials.

[0057] On the other hand, oxides containing Ni, Co, and Mn can also be used as precursors for positive electrode active materials. Therefore, in the method for producing a precursor for positive electrode active material of this disclosure, a heat treatment step S105 may be further performed.

[0058] <Heat treatment process S105> In the heat treatment step S105, a carbonate containing Ni, Co, and Mn is heat-treated to convert it into an oxide containing Ni, Co, and Mn.

[0059] For the heat treatment in step S105, a known electric furnace or the like can be used. The heat treatment temperature is preferably 300°C to 1000°C. The heat treatment time is preferably 1 hour or more, more preferably 1 hour to 48 hours, and even more preferably 5 hours to 24 hours. The heat treatment can be carried out in the atmosphere.

[0060] This heat treatment generates carbon dioxide as the carbonate is converted to an oxide. As shown in Figure 2, if this carbon dioxide is recovered and ammonium bicarbonate is synthesized using this carbon dioxide and the ammonia recovered in the ammonia removal step S102, this ammonium bicarbonate can be reused in the crystallization step S104, which is advantageous from the viewpoint of resource recycling. The recovery of carbon dioxide and the synthesis of ammonium hydrocarbons can be carried out according to known methods.

[0061] As described above, an oxide containing Ni, Co, and Mn, which is a precursor of the positive electrode active material, can be obtained. Therefore, the oxide containing Ni, Co, and Mn can be used in the production of the positive electrode active material.

[0062] As described above, according to the method for producing a cathode active material precursor of this disclosure, a cathode active material can be produced using the obtained precursor (i.e., a carbonate containing Ni, Co, and Mn, or an oxide containing Ni, Co, and Mn).

[0063] Specifically, the positive electrode active material can be produced by the method for producing a positive electrode active material precursor described above, which includes a step of obtaining a precursor (hereinafter also referred to as the "precursor preparation step") S201, a step of mixing the precursor with a lithium compound to obtain a mixture (hereinafter also referred to as the "mixing step") S202, and a step of calcining the mixture (hereinafter also referred to as the "calcination step") S203.

[0064] The precursor preparation step S201 is as described above in the description of the method for producing the cathode active material precursor in this disclosure. Therefore, the mixing step S202 will be described.

[0065] The lithium compound used in mixing step S202 serves as the Li source for the positive electrode active material. Examples of lithium compounds that can be converted to oxides by calcination include lithium carbonate, lithium nitrate, and lithium hydroxide.

[0066] The mixing ratio of the lithium compound to the precursor may be appropriately determined according to the desired composition of the positive electrode active material. For example, in the positive electrode active material, the ratio of Li to other metals (usually the sum of Ni, Co, and Mn) is preferably 0.95 to 1.15. Therefore, preferably, the lithium compound and the precursor are mixed such that the molar ratio of Li contained in the lithium compound to the metals contained in the precursor (usually the sum of Ni, Co, and Mn) is 0.95 to 1.15.

[0067] If it is desired to introduce a metal other than Li (also called another metal) that is not present in the precursor into the positive electrode active material, other metal sources may be further mixed in according to known methods.

[0068] The mixing of lithium compounds and precursors can be carried out according to known methods. For example, the precursor and lithium compound can be mixed using a mixing device such as a shaker mixer, V blender, ribbon mixer, Julia mixer, or Redige mixer. This will yield a mixture.

[0069] Next, the firing process S203 will be described. The firing process S203 can be carried out according to a known method. For example, the firing of the mixture can be carried out using a known electric furnace or the like. As for the firing atmosphere, an oxidizing atmosphere is preferred from the viewpoint of suppressing oxygen vacancies in the positive electrode active material. A suitable oxidizing atmosphere is an atmosphere with an oxygen concentration of 10% by volume or more, which may be an air atmosphere or an oxygen atmosphere (i.e., an atmosphere with a higher oxygen concentration than air). The firing temperature is 650°C to 1000°C, preferably 700°C to 900°C. The firing time is 3 hours to 8 hours, preferably 3.5 hours to 7.5 hours.

[0070] In this case, when a carbonate is used as a precursor for the positive electrode active material, carbon dioxide is generated when the lithium compound and carbonate react during calcination. If this carbon dioxide is recovered and ammonium bicarbonate is synthesized using this carbon dioxide and the ammonia recovered in the ammonia removal step S102, this ammonium bicarbonate can be reused in the crystallization step S104, which is advantageous from the viewpoint of resource recycling. The recovery of carbon dioxide and the synthesis of ammonium hydrocarbons can be carried out according to known methods.

[0071] As described above, a positive electrode active material can be manufactured. The positive electrode active material can be used in lithium-ion secondary batteries according to known methods.

[0072] The following describes examples relating to this disclosure in detail, but this disclosure is not intended to be limited to those shown in such examples.

[0073] [Example 1] First, the roasted black mass of the leaching sample was prepared using the following procedure: Lithium nickel cobalt manganese composite oxide (LiNi) was placed on an aluminum (Al) foil. 0.6 Co 0.2 Mn 0.2 A positive electrode having a positive electrode active material layer containing O2 was crushed. The crushed positive electrode material was sieved through a 500 μm mesh sieve to produce positive electrode powder. A negative electrode having a negative electrode active material layer containing graphite on a copper foil was also crushed. The crushed negative electrode material was sieved through a 500 μm mesh sieve to produce negative electrode powder. The obtained positive electrode powder and negative electrode powder were mixed to obtain black mass. This black mass was roasted at 750°C for 6 hours in a low-oxygen atmosphere to obtain roasted black mass in which most of the metal was reduced.

[0074] Next, an aqueous ammonia solution (i.e., the aqueous phase) was prepared by mixing 28% by mass aqueous ammonia with ammonium sulfate ((NH4)2SO4) as a pH adjuster.

[0075] The above-mentioned roasted black trout was added to the ammonia aqueous solution. Next, while maintaining the temperature of the ammonia aqueous solution at 80°C, leaching was performed by stirring at a stirring speed of 500 rpm for 3 hours. After that, solid-liquid separation was performed by filtration to obtain the leachate (i.e., aqueous phase) and solid residue.

[0076] The resulting aqueous phase was heated at 90°C for 3 hours while being stirred at a stirring speed of 600 rpm in an open atmosphere. This caused ammonia to volatilize from the aqueous phase. The aqueous phase was then allowed to cool to room temperature. The pH of the aqueous phase at this time was 7.8.

[0077] A saturated manganese sulfate solution was prepared. This saturated manganese sulfate solution was added to the aqueous phase and mixed. The amount of saturated manganese sulfate solution added was such that the molar ratio of Ni, Co, and Mn in the resulting aqueous phase was 6:2:2. At this time, it was visually confirmed that there were no precipitates.

[0078] A saturated aqueous solution of ammonium bicarbonate was prepared. This saturated aqueous solution of ammonium bicarbonate was added to the resulting aqueous phase containing Ni, Co, and Mn over 2 hours while stirring at 600 rpm, and crystallization was carried out. The amount of saturated aqueous solution of ammonium bicarbonate added was 2.5 molar times the total amount of Ni, Co, and Mn. At this time, the solution became cloudy due to the formation of precipitates.

[0079] The resulting mixture was separated into solid and liquid components by filtration. The precipitate was washed with water until the washing solution became clear, then dried and the precipitate was collected.

[0080] The obtained precipitate was analyzed by scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS). As a result, Ni, Co, Mn, O, and C were detected in the precipitate. Therefore, it was determined that a carbonate containing Ni, Co, and Mn was obtained.

[0081] [Example 2] A carbonate containing Ni, Co, and Mn was obtained in the same manner as in Example 1, except that the heating time for volatilizing ammonia was changed from 3 hours to 6 hours. The pH of the aqueous phase after volatilizing ammonia was 7.1.

[0082] [Example 3] A carbonate containing Ni, Co, and Mn was obtained in the same manner as in Example 1, except that the heating time for volatilizing ammonia was changed from 3 hours to 9 hours. The pH of the aqueous phase after volatilizing ammonia was 6.8.

[0083] [Evaluation of precipitation rate] The amounts of Ni, Co, and Mn in the obtained aqueous phase containing Ni, Co, and Mn before crystallization were determined by high-frequency inductively coupled plasma (ICP) emission spectroscopy. In each example, after dissolving the obtained precipitate in acid, the amounts of Ni, Co, and Mn contained in the precipitate were determined by ICP emission spectroscopy. The ratio of the total amount of Ni, Co, and Mn contained in the precipitate to the total amount of Ni, Co, and Mn contained in the aqueous phase before crystallization was calculated as a percentage, and this value was defined as the crystallization rate (%). The results are shown in Table 1.

[0084] [Table 1]

[0085] From the results above, it can be seen that the manufacturing method disclosed herein makes it possible to actually produce a precursor of the positive electrode active material.

[0086] The specific examples of this disclosure have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples described above.

[0087] In other words, the method for producing the precursor of the positive electrode active material of this disclosure is as described in the following sections [1] to [8]. [1] A step of contacting a raw material containing Ni and Co with an aqueous phase containing ammonia and ammonium sulfate to leach Ni and Co into the aqueous phase. A step of removing ammonia while recovering it from the aqueous phase, A step of dissolving a manganese salt in the aqueous phase from which ammonia has been removed, and The process involves crystallizing the aqueous phase containing the dissolved manganese salt using ammonium bicarbonate to obtain a carbonate containing Ni, Co, and Mn. A method for producing a precursor of a positive electrode active material having the following characteristics. [2] The manufacturing method according to item [1], wherein the raw material containing Ni and Co is black mass obtained by crushing and roasting used lithium-ion secondary batteries. [3] The method of production according to item [1] or [2], wherein the manganese salt is manganese sulfate. [4] The raw material containing Ni and Co further contains Mn, The manufacturing method according to any one of items [1] to [3], wherein the Mn in the manganese salt is Mn recovered from the solid residue generated in the step of leaching Ni and Co into the aqueous phase. [5] The manufacturing method according to any one of items [1] to [4], wherein the step of recovering and removing ammonia is carried out until the pH of the aqueous phase is less than 7.5. [6] The manufacturing method according to any one of items [1] to [5], wherein the ammonia recovered in the step of removing ammonia while recovering it is reused in the step of leaching Ni and Co into the aqueous phase. [7] A manufacturing method according to any one of items [1] to [6], wherein the ammonia and ammonium sulfate contained in the aqueous phase after carrying out the step of obtaining a carbonate containing Ni, Co and Mn are reused in the step of leaching Ni and Co into the aqueous phase. [8] The manufacturing method according to any one of items [1] to [7], further comprising the step of heat-treating the carbonate containing Ni, Co and Mn to obtain an oxide containing Ni, Co and Mn.

Claims

1. A step of contacting a raw material containing Ni and Co with an aqueous phase containing ammonia and ammonium sulfate to leach Ni and Co into the aqueous phase. A step of removing ammonia while recovering it from the aqueous phase, A step of dissolving a manganese salt in the aqueous phase from which ammonia has been removed, and The process involves crystallizing the aqueous phase in which the manganese salt is dissolved using ammonium bicarbonate to obtain a carbonate containing Ni, Co, and Mn. A method for producing a precursor of a positive electrode active material having the following characteristics.

2. The manufacturing method according to claim 1, wherein the raw material containing Ni and Co is black mass obtained by crushing and roasting used lithium-ion secondary batteries.

3. The manufacturing method according to claim 1, wherein the manganese salt is manganese sulfate.

4. The raw material containing Ni and Co further contains Mn, The manufacturing method according to claim 1, wherein the Mn in the manganese salt is Mn recovered from the solid residue generated in the step of leaching Ni and Co into the aqueous phase.

5. The manufacturing method according to claim 1, wherein the step of recovering and removing ammonia is carried out until the pH of the aqueous phase becomes less than 7.

5.

6. The manufacturing method according to claim 1, wherein the ammonia recovered in the step of removing ammonia while recovering it is reused in the step of leaching Ni and Co into the aqueous phase.

7. The manufacturing method according to claim 1, wherein the ammonia and ammonium sulfate contained in the aqueous phase after carrying out the step of obtaining a carbonate containing Ni, Co and Mn are reused in the step of leaching Ni and Co into the aqueous phase.

8. The manufacturing method according to claim 1, further comprising the step of heat-treating the carbonate containing Ni, Co, and Mn to obtain an oxide containing Ni, Co, and Mn.

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