Method for recovering lithium, method for producing lithium-containing solid component, and method for recovering lithium element

Abstract

The method according to the present invention comprises: a dissolution step in which a lithium (Li) element-containing compound is mixed with an aqueous solution to obtain an aqueous lithium solution; a recovery step for recovering a solid component containing a lithium (Li) element from the aqueous lithium solution; and a cleaning step for cleaning the solid component with an aqueous solution. The cleaning step is preferably configured from n stages from the first cleaning step to the nth cleaning step (n is a natural number of 2 or more). It is also preferable that the cleaning waste liquid generated in the first cleaning step be used as an aqueous liquid mixed with the compound in the dissolution step. It is also preferable that the cleaning waste liquid generated in the p-th cleaning step be used as an aqueous liquid mixed with a compound in the dissolution step, or that the cleaning waste liquid generated in the p-th cleaning step be used in the cleaning of solid components in the (p-m)-th cleaning step (p is a natural number from 2 to n, and m is a natural number from 1 to less than p).

Description

Technical Field

[0001] This invention relates to lithium recovery methods, methods for manufacturing lithium-containing solid components, and methods for recovering lithium elements. Background Technology

[0002] In recent years, secondary batteries have attracted attention as a countermeasure to prevent global warming by reducing CO2. Among them, lithium solid-state batteries using solid electrolytes are being developed as batteries that combine safety and high performance.

[0003] However, the developments conducted to date have mainly focused on improving the performance of lithium solid-state batteries and their manufacturing methods. For example, there has been insufficient development of technologies related to the reuse of waste lithium solid-state batteries and the reuse of substandard materials that cannot be used as products.

[0004] Patent document 1 proposes a method for recovering lithium by decomposing a lithium-ion secondary battery to recover a sulfide-based solid electrolyte, thereby dissolving the lithium contained in the sulfide-based solid electrolyte and recovering lithium.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2010-40458 Summary of the Invention

[0008] However, according to the method described in Patent Document 1, although lithium with a certain degree of purity can be recovered, the proportion of impurities is high and it is not suitable for reuse as one of the raw materials for solid electrolytes.

[0009] Therefore, the objective of this invention is to provide a method for recovering lithium from lithium-containing compounds in high purity.

[0010] This invention addresses the aforementioned problems by providing a lithium recovery method, the method comprising:

[0011] The dissolution process involves mixing a compound containing lithium (Li) with an aqueous solution to obtain a lithium aqueous solution.

[0012] The recycling process recovers the solid components containing lithium (Li) from the aforementioned lithium aqueous solution; and

[0013] The cleaning process involves using a water-based liquid to clean the aforementioned solid components. Attached Figure Description

[0014] Figure 1 This is a flowchart of one embodiment of the method of the present invention. Detailed Implementation

[0015] This invention relates to a method for recovering lithium from lithium-containing compounds. The method of this invention preferably includes the following steps.

[0016] The dissolution process involves mixing a compound containing lithium (Li) with an aqueous solution to obtain a lithium aqueous solution.

[0017] The recycling process recovers solid components containing Li from the aforementioned lithium aqueous solution.

[0018] The cleaning process involves using a water-based liquid to clean the aforementioned solid components.

[0019] The dissolution, recovery, and cleaning processes are performed sequentially. After the dissolution process is completed, the desulfurization, phosphorus removal, and calcium removal processes (described later) are preferably performed as needed.

[0020] After the cleaning process is completed, it is preferable to carry out a process to recover the solid components containing Li with improved purity and to utilize the cleaning waste liquid.

[0021] The following is for reference Figure 1 The flowchart shown illustrates an example of the method of the present invention.

[0022] like Figure 1 As shown, the dissolution process S101 is performed first. In the dissolution process S101, an aqueous solution (hereinafter also referred to as "lithium aqueous solution") is obtained, which is the target for Li element recovery. This aqueous solution contains a compound containing Li element (hereinafter also referred to as "lithium-containing compound") and an aqueous solution. In the lithium aqueous solution, Li element can mainly be recovered as lithium ions (Li... + The state of ) exists.

[0023] The lithium-containing compound can be any compound without limitation, as long as it contains at least Li. Examples of lithium-containing compounds include, but are not limited to, lithium oxides, hydroxides, sulfides, salts, and halides. The lithium-containing compound used in this invention preferably has water solubility. This is because it is possible to prepare a lithium aqueous solution containing a high concentration of lithium, from which Li can be recovered in high purity. Examples of water-soluble lithium-containing compounds include lithium sulfides.

[0024] In this specification, "aqueous liquid" refers to a liquid (solution, dispersion, emulsion, etc.) containing 5% by mass or more of water. The amount of water contained in the aqueous liquid is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably 99% by mass or more, and can also be 100% by mass. The aqueous liquid used in the dissolution step S101 can be, for example, water, an aqueous solution containing lithium carbonate, or the cleaning waste liquid described later. Among these, an aqueous solution containing lithium carbonate is preferred.

[0025] Lithium-containing compounds can contain other elements besides lithium. Examples of these other elements include phosphorus (P), sulfur (S), and halogens (X). Examples of lithium-containing compounds containing lithium, P, S, and X include those derived from Li. 7-x PS 6-x Cl y Br z (x represents a number where x = y + z and 1.0 < x ≤ 1.8, y represents a number where 0.3 ≤ y ≤ 1.5, and z represents a number where 0.3 ≤ z ≤ 1.5), Li 7-x-2y PS 6-x-y Cl x (x represents a number where 0.8 ≤ x ≤ 1.7, and y represents a number where 0 < y ≤ -0.25x + 0.5), Li 7-x PS 6-x X x (x represents a number from 0.2 to 1.8), Li₂S-P₂S₅-LiX and Li a PS b X c (X represents at least one halogen element, a represents a number greater than or equal to 3.0 and less than 6.0, b represents a number greater than or equal to 3.5 and less than 4.8, and c represents a number greater than or equal to 0.1 and less than 3.0) represents a compound.

[0026] In the dissolution step S101, after preparing the above raw materials, the lithium-containing compound is mixed with an aqueous solution to obtain a lithium aqueous solution. The mixing conditions are appropriately selected according to the types of lithium-containing compound and aqueous solution. Mixing can be carried out at room temperature or under heating conditions.

[0027] The lithium aqueous solution can be, for example, the leachate from substandard batteries and / or the leachate from battery waste. When using this leachate as the lithium aqueous solution, in the dissolution step S101, for example, a solid electrolyte containing Li can be recovered from the lithium solid-state battery and used as a lithium-containing compound. Recovery can be performed by removing the negative and positive electrodes from the lithium solid-state battery. The lithium aqueous solution can be obtained by mixing the solid electrolyte with an aqueous solution. During leaching, treatment with various acids and / or alkalis can be performed as needed.

[0028] From the perspective of achieving a balance between the solubility of lithium-containing compounds and the recovery efficiency of Li element, lithium aqueous solutions are generally preferably controlled with the concentration of Li element in a manner that contains more than 2.0 g / L and less than 31.0 g / L.

[0029] Lithium aqueous solutions may also contain other elements besides Li, such as metallic or non-metallic elements. Examples of such elements include, for instance, non-metallic elements like P, S, and X. Examples of metallic elements besides Li include, for instance, cobalt (Co), nickel (Ni), and manganese (Mn). These elements can originate from lithium-containing compounds and / or aqueous solutions.

[0030] When the lithium aqueous solution contains other elements, the lithium aqueous solution typically contains more than 10.0 g / L and less than 220.0 g / L of the other elements.

[0031] If the lithium aqueous solution contains solids originating from batteries that have had their solid electrolytes recycled, it is preferable to remove these solids as needed. For example, the solids can be removed by performing solid-liquid separation on the lithium aqueous solution through filtration or the like.

[0032] In the case where the lithium aqueous solution contains sulfur (S), an acid is added to the lithium aqueous solution in the desulfurization step S102. The purpose of adding the acid is to convert any sulfur that may be present in the lithium aqueous solution into hydrogen sulfide and remove it from the lithium aqueous solution. For this purpose, it is preferable to use an acid with a water solubility of 50 g / 100 g or more at the liquid temperature during the desulfurization step S102. Examples of such acids include hydrohalic acids such as hydrofluoric acid, hydrochloric acid, hydrobromic acid, and hydroiodic acid, as well as various inorganic acids such as sulfuric acid and nitric acid. One hydrohalic acid can be used alone, or two or more can be used in combination. Among these acids, hydrochloric acid is particularly preferred from the viewpoint of balancing ease of operation and solubility.

[0033] It is preferable to adjust the pH of the lithium aqueous solution by adding an acid. This effectively removes sulfur (S) from the lithium aqueous solution. From this viewpoint, it is preferable to adjust the pH of the lithium aqueous solution to -1.0 or higher, and more preferably to 0.0 or higher. Furthermore, from the same viewpoint, it is preferable to adjust the pH of the lithium aqueous solution to 2.0 or lower, and more preferably to 1.0 or lower. Various acids described above can be used for pH adjustment, with hydrochloric acid being particularly preferred. When adjusting the pH, it is preferable to also adjust the temperature of the lithium aqueous solution. From the viewpoint of more effectively removing S from the lithium aqueous solution, it is preferable to adjust the temperature of the lithium aqueous solution to 20°C or higher, more preferably to 50°C or higher, and even more preferably to 65°C or higher. Furthermore, from the same viewpoint, it is preferable to adjust the temperature of the lithium aqueous solution to 90°C or lower, more preferably to 80°C or lower, and even more preferably to 75°C or lower.

[0034] The amount of acid added to the lithium aqueous solution can be appropriately adjusted so that the pH of the lithium aqueous solution is within the aforementioned range.

[0035] In cases where the lithium aqueous solution also contains phosphorus (P), a compound containing calcium (hereinafter also referred to as a "calcium-containing compound") is added to the lithium aqueous solution in the phosphorus removal step S103. The purpose of adding the calcium-containing compound is to convert any P present in the lithium aqueous solution into a solid component containing calcium phosphate, which is then removed from the lithium aqueous solution. As the calcium-containing compound, it is preferable to use a compound that does not significantly affect the purity of the final recovered solid component containing lithium. Examples of such calcium-containing compounds include calcium carbonate and calcium chloride. One calcium-containing compound may be used alone, or two or more may be used in combination. From the viewpoint of ease of operation, calcium carbonate is particularly preferred among these calcium-containing compounds.

[0036] The term "P element that may be contained in the lithium aqueous solution" as used herein includes both P element derived from lithium-containing compounds and P element initially contained in the aqueous solution prepared in the dissolution step S101. Therefore, this step may be omitted when using lithium-containing compounds that do not contain P element and / or when preparing an aqueous solution that does not contain P element.

[0037] The amount of calcium-containing compound added to the lithium aqueous solution is preferably set within a specified range. Specifically, from the viewpoint of reliably removing phosphorus (P) from the lithium aqueous solution in the phosphorus removal step S103, the amount of calcium (Ca) in the calcium-containing compound is preferably 1.5 moles or more relative to 1 mole of P in the lithium aqueous solution. Furthermore, from the viewpoint of being able to recover Li with high purity, the amount of calcium (Ca) in the calcium-containing compound is preferably 5.0 moles or less relative to 1 mole of P in the lithium aqueous solution, more preferably 4.0 moles or less, and even more preferably 3.5 moles or less.

[0038] Before adding a calcium-containing compound to the lithium aqueous solution, the temperature of the lithium aqueous solution can be adjusted. This allows for the effective removal of phosphorus (P) from the lithium aqueous solution. From this perspective, it is preferable to adjust the temperature of the lithium aqueous solution to 20°C or higher, more preferably 40°C or higher, and even more preferably 60°C or higher. Furthermore, from the same perspective, it is preferable to adjust the temperature to 85°C or lower, more preferably 80°C or lower, and even more preferably 75°C or lower.

[0039] In the phosphorus removal process S103, the solid components containing calcium phosphate generated in the lithium aqueous solution can be removed by solid-liquid separation, for example, through filtration of the lithium aqueous solution.

[0040] Following the phosphorus removal step S103, a calcium removal step S104 is performed. The lithium aqueous solution following the phosphorus removal step S103 contains Li and Ca elements. In the calcium removal step S104, the pH of the lithium aqueous solution is adjusted. This allows for the efficient generation of a Li-containing solid component in the subsequent recovery step S105. Furthermore, any Ca elements present in the lithium aqueous solution can be converted into a calcium-containing solid component and removed from the lithium aqueous solution. The Ca elements referred to here include both the Ca elements contained in the aqueous solution or lithium-containing compound prepared in the dissolution step S101 and the Ca elements derived from the calcium-containing compound used in the phosphorus removal step S103. In other words, the purpose of this step is to remove Ca elements from the system. Therefore, this step can be omitted, for example, if the aqueous solution and lithium-containing compound do not contain Ca elements, or if the phosphorus removal step S103 is not performed.

[0041] In the calcium removal step S104, it is preferable to adjust the pH of the lithium aqueous solution to 8.0 or higher, more preferably to 9.0 or higher, and even more preferably to 9.5 or higher. Furthermore, it is preferable to adjust the pH to 12.0 or lower, more preferably to 11.0 or lower, and even more preferably to 10.5 or lower. By adjusting the pH to this range, the generation of solid components containing Li can be efficiently carried out in the next step, the recovery step S105, thereby converting the Ca element contained in the lithium aqueous solution into calcium-containing solid components and removing them from the lithium aqueous solution. Various pH adjusters, such as sodium hydroxide, can be used for pH adjustment. The pH adjuster is appropriately selected based on the pH of the lithium aqueous solution.

[0042] When sodium hydroxide is used as a pH adjuster, a solid component containing calcium hydroxide is produced in an aqueous lithium solution.

[0043] When using sodium hydroxide as a pH adjuster, the amount of pH adjuster added to the lithium aqueous solution is preferably set within a specified range. Specifically, from the viewpoint of reliably removing Ca from the lithium aqueous solution in the calcium removal step S104, the amount of hydroxide ions in the pH adjuster is preferably 2.0 moles or more relative to 1 mole of Ca in the lithium aqueous solution. Furthermore, from the viewpoint of being able to recover Li with high purity, the amount of hydroxide ions in the pH adjuster is preferably 3.0 moles or less relative to 1 mole of Ca in the lithium aqueous solution, more preferably 2.8 moles or less, and even more preferably 2.5 moles or less.

[0044] In the calcium removal process S104, the calcium-containing solid components generated in the lithium aqueous solution can be removed by solid-liquid separation, for example, through filtration of the lithium aqueous solution.

[0045] Following the calcium removal step S104, a recovery step S105 is performed. The lithium aqueous solution following the calcium removal step S104 contains Li. In the recovery step S105, a water-soluble carbonate or carbon dioxide is added to the lithium aqueous solution. The purpose of adding the water-soluble carbonate or carbon dioxide is to convert the Li contained in the lithium aqueous solution into a solid component containing Li (hereinafter also referred to as "lithium-containing solid component"), which is then recovered from the lithium aqueous solution. For this purpose, when using a water-soluble carbonate, it is preferable to use a water-soluble carbonate with a solubility in water of 22.0 g / 100 g or more at the liquid temperature during the recovery step S105. Examples of such water-soluble carbonates include sodium carbonate. One type of water-soluble carbonate can be used alone, or two or more can be used in combination. From the viewpoint of ease of operation and low risk of becoming a new source of impurities, sodium carbonate is particularly preferred as the water-soluble carbonate used in this recovery step. When sodium carbonate is used as a water-soluble carbonate, a solid component containing lithium carbonate is produced in an aqueous lithium solution.

[0046] The amount of water-soluble carbonate added to the lithium aqueous solution is preferably set within a specified range. Specifically, from the viewpoint of reliably generating a lithium-containing solid component in the lithium aqueous solution in the recovery step S105, the amount of carbonate ions in the water-soluble carbonate is preferably 0.5 moles or more relative to 1 mole of Li element in the lithium aqueous solution. Furthermore, from the viewpoint of being able to recover Li element with high purity, the amount of carbonate ions in the water-soluble carbonate is preferably 1.0 moles or less relative to 1 mole of Li element in the lithium aqueous solution, more preferably 0.8 moles or less, and even more preferably 0.6 moles or less.

[0047] On the other hand, when using carbon dioxide, the amount of carbon dioxide bubbled in the lithium aqueous solution is preferably sufficient to convert the Li element contained in the lithium aqueous solution into a lithium-containing solid component.

[0048] When adding water-soluble carbonates or carbon dioxide to an aqueous lithium solution, it is preferable to adjust the temperature of the aqueous lithium solution. This allows for the efficient generation of lithium-containing solid components in the aqueous lithium solution. From this viewpoint, it is preferable to adjust the temperature of the aqueous lithium solution to, for example, 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. Furthermore, from the same viewpoint, it is preferable to adjust the temperature of the aqueous lithium solution to, for example, 90°C or lower, more preferably 85°C or lower, and even more preferably 80°C or lower.

[0049] In the recovery step S105, the lithium-containing solid components generated in the lithium aqueous solution can be recovered through solid-liquid separation, such as by filtering the lithium aqueous solution. In this way, the lithium-containing solid components are concentrated from the lithium aqueous solution. The liquid component from which the solid components have been separated from the lithium aqueous solution in the recovery step S105 contains, for example, halide ions contained in the lithium aqueous solution prepared in the dissolution step S101, halide ions from the acid used in the desulfurization step S102, and sodium ions from the water-soluble carbonate used in the recovery step S105.

[0050] Next, in cleaning step S106, the lithium-containing solid component is cleaned with an aqueous solution. In cleaning step S106, the aqueous solution is brought into contact with the lithium-containing solid component. The type of aqueous solution is as described above. Through contact, impurities contained in the lithium-containing solid component dissolve in the aqueous solution. These impurities include, for example, the halide ions and sodium ions mentioned above. The aqueous solution containing impurities is recycled as cleaning waste liquid. Through this process, residual impurities in the lithium-containing solid component can be removed, allowing for the recovery of Li element with high purity. Details of the aqueous solution used in cleaning step S106 will be described later.

[0051] There are no particular limitations on the cleaning method for lithium-containing solid components, and any method known to date can be used. From the viewpoint of balancing the ease of the cleaning method with the level of cleaning force, it is preferable to perform reslurry cleaning or cleaning within a filtration device in cleaning step S106.

[0052] In the case of re-slurry cleaning, the lithium-containing solid components recovered in the recycling process S105 are added to an aqueous solution to form a slurry for cleaning. Therefore, the aqueous solution easily covers the lithium-containing solid components. This effectively cleans the entire lithium-containing solid component.

[0053] Cleaning within the filtration device can be performed, for example, as follows: the lithium-containing solid components recovered in the recovery process S105 are placed into a filtration device with a discharge function, and an aqueous liquid is circulated into the filtration device to clean the filter cake. After cleaning, the aqueous liquid is discharged from the filtration device using the discharge function. According to this method, the cleaning process can be completed simply by circulating an aqueous liquid into the filtration device, thus eliminating the need for additional equipment such as a resizing tank, which is therefore preferable.

[0054] Both reslurry cleaning and filtration devices can effectively clean lithium-containing solid components. From the viewpoint of further reducing the amount of impurities in lithium-containing solid components, reslurry cleaning is preferred.

[0055] In the cleaning process S106, from the viewpoint of recovering Li element with high purity, it is preferable to use an aqueous solution adjusted to a specified temperature for cleaning. Specifically, it is preferable to adjust the temperature of the aqueous solution during cleaning to 55°C or higher, more preferably to 60°C or higher, and even more preferably to 65°C or higher. Furthermore, from the same viewpoint, it is preferable to adjust the temperature of the aqueous solution during cleaning to 80°C or lower, and more preferably to 75°C or lower.

[0056] The cleaning of lithium-containing solid components should preferably be carried out thoroughly until the concentration of impurities in the cleaning wastewater generated during the cleaning process is below a predetermined value. Whether this concentration is below the predetermined value can be determined by measuring the concentration of impurities in the cleaning wastewater using the impurity concentration determination step S107 after cleaning the lithium-containing solid components.

[0057] In the impurity concentration determination step S107, halide ions and / or sodium ions are used as the measurement targets, for example. In this invention, through each step up to the recovery step S105, impurities other than halide ions and sodium ions are sufficiently removed from the lithium aqueous solution. Therefore, by using halide ions and / or sodium ions as the measurement targets, based on the result that the combined concentration of the two ions is below a predetermined value, it can be determined that the lithium-containing solid component contains few impurities, that is, Li element is concentrated in the lithium-containing solid component. Alternatively, it can also be determined that Li element is concentrated in the lithium-containing solid component based on the result that the concentrations of halide ions and sodium ions are each below a predetermined value.

[0058] The concentrations of halide ions and sodium ions in the cleaning wastewater can be determined, for example, by the following methods. Specifically, the concentration of halide ions can be determined using inductively coupled plasma atomic emission spectrometry (ICP-AES) and / or ion chromatography. Additionally, the concentration of sodium ions can be determined using atomic absorption spectrometry and / or ICP-AES. Alternatively, qualitative concentration variations of halide ions and sodium ions can also be confirmed using ion electrode methods.

[0059] In this invention, it is preferable to perform cleaning until the total concentration of halide ions and sodium ions in the cleaning waste liquid is, for example, 0.100 g / L or less, more preferably until it is 0.070 g / L or less, further preferably until it is 0.030 g / L or less, and even more preferably until it is 0.010 g / L or less. The lower the total concentration of halide ions and sodium ions in the cleaning waste liquid, the more preferred it is; for example, it can be 0.005 g / L or more.

[0060] The concentration of halide ions in the cleaning waste liquid is preferably 0.030 g / L or less, more preferably 0.020 g / L or less, even more preferably 0.010 g / L or less, even more preferably 0.005 g / L or less, and particularly preferably 0.002 g / L or less. A lower concentration of halide ions in the cleaning waste liquid is preferred; for example, it can be 0.001 g / L or more. When the cleaning waste liquid contains two or more types of halide ions, "concentration of halide ions in the cleaning waste liquid" refers to the total concentration of halide ions contained in the cleaning waste liquid.

[0061] The concentration of sodium ions in the cleaning waste liquid is preferably 0.050 g / L or less, more preferably 0.010 g / L or less, even more preferably 0.005 g / L or less, and even more preferably 0.002 g / L or less. The lower the concentration of sodium ions in the cleaning waste liquid, the more preferred it is; for example, it can be 0.001 g / L or more.

[0062] In the determination step S107 of the impurity concentration, if the measured concentration is below the aforementioned value, it is determined that the lithium-containing solid component concentrated with Li element has been recovered (purification product recovery step S108), and the method of the present invention can be terminated. In the purification product recovery step S108, the cleaning waste liquid generated during cleaning is recovered simultaneously with the recovery of the lithium-containing solid component. This cleaning waste liquid can be used in the cleaning waste liquid utilization step S109 described later. Conversely, if the measured total concentration exceeds the aforementioned value, it is determined that the lithium-containing solid component contains a large amount of impurities, and the process returns to the cleaning step S106, where the lithium-containing solid component can be cleaned again. The cleaning step S106 and the impurity concentration determination step S107 can be repeated any number of times until the concentration measured in the impurity concentration determination step S107 becomes below the aforementioned value. When performing the cleaning step S106 multiple times, the cleaning time of the lithium-containing solid component can be varied in each iteration.

[0063] When the cleaning step S106 is repeated, this step S106 can consist of n stages from the first cleaning step to the nth cleaning step. n is a natural number of 2 or more. From the viewpoint of ensuring that the combined concentration of halide ions and sodium ions in the cleaning waste liquid is below a predetermined value, and from the viewpoint of concentrating Li element in the lithium-containing solid component, n is typically 2 or more, and more preferably 3 or more. The larger the value of n, the easier it is to determine the impurity concentration in the determination step S107, but it can also be 5 or less.

[0064] One feature of the method of the present invention is that it includes a step of cleaning lithium-containing solid components and a step of utilizing cleaning waste liquid.

[0065] In the case of recovering Li from waste lithium solid-state batteries and / or substandard materials, the purity of Li must be at least a certain value in order to reuse the Li as a raw material for solid electrolytes. While the method described in Patent Document 1 has been reported as a method for recovering Li, this method suffers from insufficient concentration of the recovered Li, resulting in the inability to obtain Li of a purity suitable for reuse. In contrast, as described above, the method of the present invention, which includes a step of cleaning the lithium-containing solid component with an aqueous solution, can improve the purity of Li in the lithium-containing solid component, enabling the recovery of high-purity Li suitable for reuse as a raw material for solid electrolytes. Furthermore, the method of the present invention, as described below, includes a cleaning wastewater utilization step S109 that utilizes the cleaning wastewater generated during the cleaning process, thus enabling the recovery of Li that accidentally flows into the cleaning wastewater, and allowing for the obtaining of Li at a higher yield.

[0066] In the wastewater utilization step S109, the concentration of impurities in the wastewater is first determined. The objects of measurement are the same as in the impurity concentration determination step S107, for example, halide ions and / or sodium ions. When the wastewater contains excessive impurities, these impurities may sometimes circulate in the various steps of the invention, and may unexpectedly accumulate in the lithium-containing solid components. Therefore, from the viewpoint of recovering Li element in a high yield, it is preferable to determine the concentration of impurities in the wastewater and selectively utilize the wastewater with a concentration below a predetermined value. For this reason, the combined concentration of halide ions and sodium ions in the wastewater generated in the wastewater utilization step S109 is preferably, for example, 10.0 g / L or less, more preferably 1.0 g / L or less, and even more preferably 0.1 g / L or less. When the wastewater is used in the final cleaning step S106, the combined concentration of halide ions and sodium ions in the wastewater is particularly preferably, for example, 0.1 g / L or less.

[0067] If it can be confirmed that the concentration of impurities in the cleaning waste liquid is below a predetermined value, the cleaning waste liquid can be utilized in a process prior to the cleaning waste liquid utilization step S109. The method of the present invention may include multiple steps for removing impurities that may be present in the lithium aqueous solution and the lithium-containing solid component. The cleaning step S106, which generates the cleaning waste liquid, is located downstream of the impurity removal step. Therefore, from the viewpoint of preventing the concentration of Li element into the lithium-containing solid component from being hindered by impurities that may be present in the cleaning waste liquid, it is preferable to determine the step of utilizing the cleaning waste liquid as described above. Furthermore, it is also preferable that by utilizing the cleaning waste liquid, Li element that accidentally flows into the cleaning waste liquid can be recovered.

[0068] If the concentration of impurities in the cleaning waste liquid exceeds the specified value, the cleaning waste liquid may be discarded without being returned to the system (disposal process S110).

[0069] The following description uses the case where the cleaning process consists of n stages as an example to illustrate the cleaning wastewater utilization process S109. As described above, when the cleaning process S106 consists of the first cleaning process to the nth cleaning process, the cleaning wastewater generated in the first cleaning process can be used as an aqueous solution mixed with a lithium-containing compound in the dissolution process S101. By using the cleaning wastewater in the dissolution process S101, the Li element that accidentally flows into the cleaning wastewater can be recovered between the series of processes from this process S101 to the purification product recovery process S108.

[0070] The cleaning waste liquid that can be used in the dissolution step S101 is not limited to the cleaning waste liquid generated in the first cleaning step. In addition to the first cleaning step, the cleaning waste liquid generated in the p-th cleaning step can also be used as an aqueous solution mixed with a lithium-containing compound in the dissolution step S101. p is a natural number of 2 or more and n or less. The value of p can take any value, provided it satisfies the relationship with the value of n.

[0071] The process of utilizing the cleaning waste liquid is not limited to the dissolution process S101. For example, the cleaning waste liquid generated in the p-th cleaning process can be used in the (pm)-th cleaning process for the cleaning process S106 containing lithium solid components. m is a natural number greater than or equal to 1 and less than p. The value of m can take any value, provided that it satisfies the relationship with the value of p. In the method of the present invention, by utilizing the cleaning waste liquid in the cleaning process S106 in addition to the dissolution process S101, the Li element accidentally flowing into the cleaning waste liquid can be recovered more effectively.

[0072] For these reasons, in the method of the present invention, the cleaning waste liquid generated in the p-th cleaning step can be used as an aqueous solution mixed with the lithium-containing compound in the dissolution step S101. Alternatively, the cleaning waste liquid generated in the p-th cleaning step can be used for cleaning the lithium-containing solid components in the (pm) cleaning step S106. In either case, accidental leakage of Li elements outside the steps of the method of the present invention can be avoided, and Li elements can be effectively recovered, which is therefore preferred.

[0073] In this way, lithium-containing solid components, i.e. solid components containing Li, can be recovered in high purity. The obtained solid components can be used as solid electrolytes themselves or as one of the raw materials for solid electrolytes, either in this state or after being converted into halides such as lithium chloride and lithium bromide, or sulfides such as lithium sulfide.

[0074] The present invention has been described above based on its preferred embodiments, but the present invention is not limited to the above embodiments.

[0075] Regarding the above embodiments, the following lithium recovery method, method for manufacturing lithium-containing solid components, and method for recovering lithium element are further disclosed.

[0076] [1] A lithium recovery method, comprising:

[0077] The dissolution process involves mixing a compound containing lithium (Li) with an aqueous solution to obtain a lithium aqueous solution.

[0078] The recycling process recovers the solid components containing lithium (Li) from the aforementioned lithium aqueous solution; and

[0079] The cleaning process involves using a water-based liquid to clean the aforementioned solid components.

[0080] [2] According to the lithium recovery method described in [1], the above-mentioned cleaning process consists of n stages from the first cleaning process to the nth cleaning process (n is a natural number of 2 or more).

[0081] [3] According to the lithium recovery method described in [2], the cleaning waste liquid generated in the first cleaning step is used as the aqueous liquid that is mixed with the above-mentioned compound in the above-mentioned dissolution step.

[0082] [4] According to the lithium recovery method described in [2] or [3], the cleaning waste liquid generated in the p-th cleaning step is used as the aqueous liquid mixed with the compound in the dissolution step, or the cleaning waste liquid generated in the p-th cleaning step is used for cleaning the solid components in the (pm) cleaning step (p is a natural number of 2 or more and n or less, m is a natural number of 1 or more and less than p).

[0083] [5] The lithium recovery method according to any one of [1] to [4], wherein the above-mentioned cleaning step is a re-slurry cleaning step or a cleaning step performed in a filtration device.

[0084] [6] The lithium recovery method according to any one of [1] to [5], wherein the cleaning is performed until the total concentration of halide ions and sodium ions in the cleaning waste liquid generated in the above cleaning process is less than 0.100 g / L.

[0085] [7] The lithium recovery method according to any one of [1] to [6], wherein the above compound further contains phosphorus (P) element.

[0086] [8] According to the lithium recovery method described in [7], the following step is performed after the above-mentioned dissolution step:

[0087] In the phosphorus removal process, calcium carbonate is added to the aforementioned lithium aqueous solution to remove the solid components containing calcium phosphate generated in the lithium aqueous solution; and

[0088] In the calcium removal process, following the phosphorus removal process, the pH of the lithium aqueous solution is adjusted to remove the calcium-containing solid components generated in the lithium aqueous solution.

[0089] The above-mentioned recovery process is performed after the above-mentioned calcium removal process.

[0090] [9] The lithium recovery method according to any one of [1] to [8], wherein the recovery step is to add water-soluble carbonate to the lithium aqueous solution and recover the solid component containing lithium carbonate generated in the lithium aqueous solution from the lithium aqueous solution.

[0091]

[10] A method for manufacturing a solid component containing lithium, comprising:

[0092] The dissolution process involves mixing a compound containing lithium (Li) with an aqueous solution to obtain a lithium aqueous solution.

[0093] The recycling process recovers the solid components containing lithium (Li) from the aforementioned lithium aqueous solution; and

[0094] The cleaning process involves using a water-based liquid to clean the aforementioned solid components.

[0095]

[11] A method for recovering lithium, comprising:

[0096] In the dissolution process, a solid electrolyte containing lithium (Li) is recovered from the lithium solid-state battery, and the solid electrolyte is mixed with an aqueous solution to obtain a lithium aqueous solution.

[0097] The recycling process recovers the solid components containing lithium (Li) from the aforementioned lithium aqueous solution; and

[0098] The cleaning process involves using a water-based liquid to clean the aforementioned solid components.

[0099] Example

[0100] The present invention will now be described in more detail through examples. However, the scope of the present invention is not limited to these examples. Unless otherwise specified, "%" refers to "mass %".

[0101] [Example 1]

[0102] (1) Dissolving process S101

[0103] 10.0g of Li 5.4 PS 4.4 Cl 0.4 Br 0.6 A lithium aqueous solution was prepared by mixing the lithium carbonate solution with 100 mL of a 0.14 mol / L lithium carbonate aqueous solution that simulates cleaning waste liquid.

[0104] (2) Desulfurization process S102

[0105] 15 mL of 12 mol / L hydrochloric acid was added to the lithium aqueous solution to adjust the pH to below 1. Then, the lithium aqueous solution was heated to 70°C to generate hydrogen sulfide, thus removing sulfur from the liquid.

[0106] (3) Phosphorus removal process S103

[0107] 0.12 moles of calcium carbonate were added to an aqueous lithium solution, causing calcium phosphate to precipitate. The precipitated calcium phosphate was then removed from the aqueous lithium solution using a suction filter.

[0108] (4) Calcium removal process S104

[0109] 0.2 moles of solid sodium hydroxide were added to an aqueous lithium solution to adjust the pH to 10.0. This resulted in the formation of a calcium hydroxide precipitate in the lithium solution. The precipitated calcium hydroxide was removed from the aqueous lithium solution using a suction filter.

[0110] (5) Recycling process S105

[0111] 0.14 mol of sodium carbonate was added to a lithium aqueous solution adjusted to 70°C, causing lithium carbonate to precipitate in the solution. The precipitated lithium carbonate was then recovered from the lithium aqueous solution using a suction filter.

[0112] (6) Cleaning process S106

[0113] Lithium carbonate was re-slurry-cleaned using 100 mL of a saturated aqueous solution of lithium carbonate at a temperature of 70°C.

[0114] (7) Impurity concentration determination process S107

[0115] A portion of the cleaning waste liquid generated in cleaning process S106 was recovered, and the concentrations of chloride ions, bromide ions, and sodium ions in the waste liquid were determined. The determinations were performed using an ICP-AES analyzer (model: SPS3500DD) manufactured by Hitachi Advanced Technology Co., Ltd., using the standard curve method. The results are shown in Table 1 below.

[0116] (8) Purified product recovery process S108

[0117] The lithium carbonate that was cleaned in the cleaning process S106 is recovered using a suction filter.

[0118] (Example 2)

[0119] The dissolution step S101 to the recovery step S105 are performed in the same manner as in Example 1. In the cleaning step S106, lithium carbonate is re-slurry-cleaned in two stages using a saturated aqueous solution of lithium carbonate at a liquid temperature of 70°C. Fresh saturated aqueous solution of lithium carbonate is used for both cleaning stages.

[0120] Next, the impurity concentration determination step S107 and the purified product recovery step S108 are performed in the same manner as in Example 1 to obtain lithium carbonate.

[0121] (Example 3)

[0122] The dissolution step S101 to the recovery step S105 are performed in the same manner as in Example 1. In the cleaning step S106, lithium carbonate is re-slurry-cleaned in three stages using a saturated aqueous solution of lithium carbonate at a liquid temperature of 60°C. Fresh saturated aqueous solution of lithium carbonate is used in all three cleaning stages.

[0123] Next, the impurity concentration determination step S107 and the purified product recovery step S108 are performed in the same manner as in Example 1 to obtain lithium carbonate.

[0124] [Table 1]

[0125]

[0126] As clearly shown in Table 1, washing lithium carbonate reduces the concentrations of chloride, bromide, and sodium ions in the washing waste liquid. Lower concentrations of these ions in the washing waste liquid indicate higher purity of the obtained lithium carbonate. Therefore, washing lithium carbonate improves its purity. Furthermore, repeating the washing process further enhances the purity of the lithium carbonate.

[0127] Industrial availability

[0128] According to the present invention, a method is provided that can recover lithium element in high purity from lithium-containing compounds.

Claims

1. A lithium recovery method comprising: a dissolving step of mixing a compound containing a lithium (Li) element with an aqueous solution to obtain a lithium aqueous solution; a recovery step of recovering a solid component containing a lithium (Li) element from the lithium aqueous solution; and a washing step of washing the solid component with an aqueous solution.

2. The lithium recovery method according to claim 1, wherein, The washing step is composed of n stages of a first washing step to an n-th washing step, n being a natural number of 2 or more.

3. The lithium recovery method according to claim 2, wherein, A washing waste solution produced in the first washing step is used as the aqueous solution mixed with the compound in the dissolving step.

4. The lithium recovery method according to claim 2, wherein, A washing waste solution produced in a p-th washing step is used as the aqueous solution mixed with the compound in the dissolving step, or a washing waste solution produced in the p-th washing step is used for washing of the solid component in a (p-m)-th washing step, p being a natural number of 2 or more and n or less, and m being a natural number of 1 or more and less than p.

5. The lithium recovery method according to claim 1, wherein, The washing step is a step in which repulping washing is performed, or a step in which washing is performed in a filter device.

6. The lithium recovery method according to claim 1, wherein Washing is performed until the total concentration of halide ions and sodium ions in a washing waste solution produced in the washing step becomes 0.100 g / L or less.

7. The lithium recovery method according to claim 1, wherein The compound further contains a phosphorus (P) element.

8. The lithium recovery method according to claim 7, wherein The following steps are performed after the dissolving step: a phosphorus removal step of adding calcium carbonate to the lithium aqueous solution, and removing a solid component containing calcium phosphate produced in the lithium aqueous solution from the lithium aqueous solution; and a calcium removal step of adjusting the pH of the lithium aqueous solution after the phosphorus removal step, and removing a solid component containing calcium produced in the lithium aqueous solution from the lithium aqueous solution, The recovery step is performed after the calcium removal step. The recovery step is a step of adding a water-soluble carbonate to the lithium aqueous solution, and recovering a solid component containing lithium carbonate produced in the lithium aqueous solution from the lithium aqueous solution.

9. The lithium recovery method according to claim 1, wherein, 10. A method of manufacturing a solid component containing lithium, comprising: a dissolving step of mixing a compound containing a lithium (Li) element with an aqueous solution to obtain a lithium aqueous solution; a recovery step of recovering a solid component containing a lithium (Li) element from the lithium aqueous solution; and a washing step of washing the solid component with an aqueous solution.

11. A method of recovering a lithium element, comprising: a dissolving step of recovering a solid electrolyte containing a lithium (Li) element from a lithium solid-state battery, and mixing the solid electrolyte with an aqueous solution to obtain a lithium aqueous solution; a recovery step of recovering a solid component containing a lithium (Li) element from the lithium aqueous solution; and a washing step of washing the solid component with an aqueous solution. ​

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