Lithium recovery method, production method for solid component containing lithium, and recovery method for lithium

Abstract

A method according the present invention includes: a dissolution step for obtaining an aqueous lithium solution by mixing an aqueous solution and a compound containing the element lithium (Li); a recovery step for recovering a solid component containing the element lithium (Li) from the aqueous lithium solution; and a washing step for washing the solid component with an aqueous solution. The washing step preferably comprises n stages from a first washing step to an n-th washing step (n being a natural number not less than 2). Waste washing liquid generated in the first washing step is preferably used as the aqueous solution to be mixed with the compound in the dissolution step. Preferably, waste washing liquid generated in the p-th washing step is used as the aqueous solution to be mixed with the compound in the dissolution step, or is used for washing the solid component in the (p-m)-th washing step (p being a natural number not less than 2 but not more than n, and m being a natural number not less than 1 but less than p).

Description

Lithium recovery method, method for producing solid component containing lithium, and method for recovering lithium element

[0001] The present invention relates to a method for recovering lithium, a method for producing a solid component containing lithium, and a method for recovering lithium element.

[0002] In recent years, CO ２ Secondary batteries have been attracting attention as an effort to prevent global warming by reducing CO2 emissions. Among these, lithium solid-state batteries using solid electrolytes are being developed as batteries that combine safety and high performance. However, development to date has mainly focused on improving the performance of lithium solid-state batteries and manufacturing methods for such batteries. For example, technological developments related to recycling methods for waste lithium solid-state batteries and recycling methods for non-standard materials that cannot be used in products have been insufficient.

[0003] Patent Document 1 proposes a method of recovering lithium by disassembling a lithium ion secondary battery to recover a sulfide-based solid electrolyte and dissolving the lithium contained in the sulfide-based solid electrolyte.

[0004] JP 2010-40458 A

[0005] However, although the method described in Patent Document 1 makes it possible to recover lithium with a certain degree of purity, the lithium contains a high proportion of impurities, making it unsuitable for reuse as a raw material for solid electrolytes. Therefore, an object of the present invention is to provide a method for recovering lithium element with high purity from a lithium-containing compound.

[0006] The present invention solves the above-mentioned problems by providing a method for recovering lithium, the method comprising: a dissolving step of mixing a compound containing lithium (Li) element with an aqueous liquid to obtain an aqueous lithium solution; a recovery step of recovering a solid component containing lithium (Li) element from the aqueous lithium solution; and a washing step of washing the solid component with the aqueous liquid.

[0007] FIG. 1 is a flow chart of one embodiment of the method of the present invention.

[0008] The present invention relates to a method for recovering lithium element from a lithium-containing compound. The method of the present invention preferably comprises the following steps: a dissolution step of mixing a compound containing lithium (Li) element with an aqueous liquid to obtain an aqueous lithium solution; a recovery step of recovering a solid component containing Li element from the aqueous lithium solution; and a washing step of washing the solid component with an aqueous liquid. The dissolution step, recovery step, and washing step are performed in this order. After completion of the dissolution step, it is preferable to perform a desulfurization step, a phosphorus removal step, and a calcium removal step, which will be described later, as necessary. After completion of the washing step, it is preferable to perform a step of recovering a solid component containing Li element with increased purity and a step of utilizing the washing waste liquid. An example of the method of the present invention will be described below with reference to the flowchart shown in FIG. 1.

[0009] As shown in FIG. 1, first, a dissolving step S101 is performed. In the dissolving step S101, an aqueous solution from which Li element is to be recovered (hereinafter also referred to as a "lithium aqueous solution") is obtained. This aqueous solution contains a compound containing Li element (hereinafter also referred to as a "lithium-containing compound") and an aqueous liquid. In the lithium aqueous solution, Li element is mainly converted into lithium ions (Li ＋) state. The lithium-containing compound may contain at least Li, and various compounds can be used without limitation. Examples of lithium-containing compounds include, but are not limited to, oxides, hydroxides, sulfides, salts, and halides containing lithium. The lithium-containing compound used in the present invention is preferably water-soluble. This is because a lithium aqueous solution containing a high concentration of lithium can be prepared and Li element can be recovered from the aqueous solution with high purity. An example of a water-soluble lithium-containing compound is a sulfide containing lithium. In this specification, the term "aqueous liquid" refers to a liquid (such as a solution, dispersion, or emulsion) containing 5% or more by mass of water. The amount of water contained in the aqueous liquid is preferably 95% or more by mass, more preferably 98% or more by mass, even more preferably 99% or more by mass, and may even 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 wastewater described below. Among these, an aqueous solution containing lithium carbonate is preferably used.

[0010] The lithium-containing compound may further contain other elements in addition to the Li element. Examples of other elements include phosphorus (P), sulfur (S), and halogen (X). Examples of lithium-containing compounds containing Li, P, S, and X include Li, ７－ｘ P.S. ６－ｘ Cl ｙ Br ｚ (x represents a number in the range of x = y + z and 1.0 < x ≦ 1.8, y represents a number in the range of 0.3 ≦ y ≦ 1.5, and z represents a number in the range of 0.3 ≦ z ≦ 1.5), Li ７－ｘ－２ｙ P.S. ６－ｘ－ｙ Cl ｘ (where x represents a number of 0.8≦x≦1.7, and y represents a number of 0<y≦−0.25x+0.5), Li ７－ｘ P.S. ６－ｘ X ｘ (x represents a number from 0.2 to 1.8), Li ２ S-P ２ S ５ - LiX and Li ａ P.S. ｂ X ｃ(X is at least one halogen element; a is a number of 3.0 or more and 6.0 or less; b is a number of 3.5 or more and 4.8 or less; c is a number of 0.1 or more and 3.0 or less).

[0011] In the dissolving step S101, once the above raw materials are prepared, the lithium-containing compound and the aqueous liquid are mixed to obtain a lithium aqueous solution. The mixing conditions are appropriately selected depending on the types of the lithium-containing compound and the aqueous liquid. The mixing may be performed at room temperature or while heating.

[0012] The lithium aqueous solution may be, for example, a leachate from a non-standard battery or a leachate from battery scrap. When the leachate is used as the lithium aqueous solution, in the dissolution step S101, for example, a solid electrolyte containing Li element may be recovered from a lithium solid-state battery, and the solid electrolyte may be used as the lithium-containing compound. The recovery may be performed by removing the negative electrode and the positive electrode from the lithium solid-state battery. The lithium aqueous solution may be obtained by mixing the solid electrolyte with an aqueous liquid. During the leaching, treatment with various acids or alkalis may be performed as necessary.

[0013] In general, it is preferable to control the concentration of Li element in the lithium aqueous solution so that it contains 2.0 g / L or more and 31.0 g / L or less, in terms of balancing the solubility of the lithium-containing compound and the recovery efficiency of Li element.

[0014] The lithium aqueous solution may contain other elements, such as metal elements or nonmetal elements other than Li. Examples of such elements include nonmetal elements such as P, S, and X. Examples of metal elements other than Li include cobalt (Co), nickel (Ni), and manganese (Mn). These elements may be derived from the lithium-containing compound or the aqueous solution. When the lithium aqueous solution contains other elements, the lithium aqueous solution generally contains 10.0 g / L or more and 220.0 g / L or less of the other elements.

[0015] When the lithium aqueous solution contains solid matter derived from the battery from which the solid electrolyte was recovered, it is preferable to remove the solid matter as needed. For example, the lithium aqueous solution may be subjected to solid-liquid separation by filtration or the like to remove the solid matter.

[0016] If the lithium aqueous solution contains sulfur element, 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 element contained in the lithium aqueous solution into hydrogen sulfide and remove it from the lithium aqueous solution. For this purpose, an acid having a solubility in water of 50 g / 100 g or more at the solution temperature at which the desulfurization step S102 is performed is preferably used. Examples of such acids include various inorganic acids such as hydrofluoric acid, hydrochloric acid, hydrogen halides such as hydrogen bromide and hydrogen iodide, sulfuric acid, and nitric acid. One type of hydrogen halide can be used alone, or two or more types can be used in combination. Of these acids, hydrochloric acid is particularly preferred from the viewpoint of balancing ease of handling and high solubility.

[0017] It is preferable to adjust the pH of the lithium aqueous solution by adding an acid to the lithium aqueous solution. This allows for efficient removal of the S element from the lithium aqueous solution. From this perspective, it is preferable to adjust the pH of the lithium aqueous solution to -1.0 or higher, and more preferably to adjust it to 0.0 or higher. From the same perspective, it is preferable to adjust the pH of the lithium aqueous solution to 2.0 or lower, and even more preferably to adjust it to 1.0 or lower. The various acids mentioned above can be used to adjust the pH, and among them, hydrochloric acid is particularly preferred. When adjusting the pH, it is preferable to also adjust the temperature of the lithium aqueous solution. From the perspective of more efficiently removing the S element 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. From the same perspective, 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. 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 above-mentioned range.

[0018] When the lithium aqueous solution also contains phosphorus, 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 phosphorus contained in the lithium aqueous solution into a solid component containing calcium phosphate and remove it from the lithium aqueous solution. A calcium-containing compound that does not significantly affect the purity of the solid component containing lithium that is ultimately recovered is preferably used. Examples of such calcium-containing compounds include calcium carbonate and calcium chloride. A single calcium-containing compound can be used alone, or two or more calcium-containing compounds can be used in combination. Among these calcium-containing compounds, calcium carbonate is particularly preferred from the viewpoint of ease of handling. The term "phosphorus element that may be contained in the lithium aqueous solution" as used herein encompasses both phosphorus derived from the lithium-containing compound and phosphorus originally contained in the aqueous solution prepared in the dissolution step S101. Therefore, this step may be omitted when a lithium-containing compound not containing phosphorus is used or when an aqueous solution not containing phosphorus is prepared.

[0019] The amount of the calcium-containing compound added to the lithium aqueous solution is preferably within a predetermined range. Specifically, from the viewpoint of reliably removing the P element from the lithium aqueous solution in the phosphorus removal step S103, the ratio of Ca element in the calcium-containing compound to 1 mole of P element in the lithium aqueous solution is preferably 1.5 moles or more. Furthermore, from the viewpoint of recovering Li element with high purity, the ratio of Ca element in the calcium-containing compound to 1 mole of P element in the lithium aqueous solution is preferably 5.0 moles or less, more preferably 4.0 moles or less, and even more preferably 3.5 moles or less.

[0020] Prior to adding the calcium-containing compound to the lithium aqueous solution, the temperature of the lithium aqueous solution may be adjusted. This allows the P element in the lithium aqueous solution to be efficiently removed. From this viewpoint, the temperature of the lithium aqueous solution is preferably adjusted to 20°C or higher, more preferably adjusted to 40°C or higher, and even more preferably adjusted to 60°C or higher. From the same viewpoint, the temperature is preferably adjusted to 85°C or lower, more preferably adjusted to 80°C or lower, and even more preferably adjusted to 75°C or lower.

[0021] The solid components containing calcium phosphate generated in the lithium aqueous solution in the phosphorus removal step S103 can be removed by solid-liquid separation, for example, by filtering the lithium aqueous solution.

[0022] After the phosphorus removal step S103, a calcium removal step S104 is performed. The lithium aqueous solution after 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 efficient production of a solid component containing Li in the subsequent recovery step S105. Furthermore, Ca elements that may be contained in the lithium aqueous solution can be converted into solid components containing calcium and removed from the lithium aqueous solution. The Ca element referred to here includes both the Ca element contained in the aqueous solution or lithium-containing compound prepared in the dissolution step S101 and the Ca element 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, for example, this step can be omitted if the aqueous solution and lithium-containing compound do not contain Ca elements, or if the phosphorus removal step S103 is not performed.

[0023] In the calcium removal step S104, the pH of the lithium aqueous solution is preferably adjusted to 8.0 or higher, more preferably 9.0 or higher, and even more preferably 9.5 or higher. Furthermore, the pH is preferably adjusted to 12.0 or lower, more preferably 11.0 or lower, and even more preferably 10.5 or lower. By adjusting the pH within this range, a solid component containing Li element can be efficiently produced in the subsequent recovery step S105, and further, Ca element contained in the lithium aqueous solution can be converted into a solid component containing calcium and removed from the lithium aqueous solution. Various pH adjusters, such as sodium hydroxide, can be used to adjust the pH. The pH adjuster is appropriately selected depending on the pH of the lithium aqueous solution. When sodium hydroxide, for example, is used as a pH adjuster, a solid component containing calcium hydroxide is generated in the lithium aqueous solution.

[0024] When sodium hydroxide is used as the pH adjuster, the amount of pH adjuster added to the lithium aqueous solution is preferably within a predetermined range. Specifically, from the viewpoint of reliably removing Ca element from the lithium aqueous solution in the calcium removal step S104, it is preferable that the amount of hydroxide ions in the pH adjuster is 2.0 moles or more per mole of Ca element in the lithium aqueous solution. Furthermore, from the viewpoint of recovering Li element with high purity, it is preferable that the amount of hydroxide ions in the pH adjuster is 3.0 moles or less per mole of Ca element in the lithium aqueous solution, more preferably 2.8 moles or less, and even more preferably 2.5 moles or less.

[0025] The calcium-containing solid component generated in the lithium aqueous solution in the calcium removal step S104 can be removed by solid-liquid separation, for example, by filtering the lithium aqueous solution.

[0026] After the calcium removal step S104, a recovery step S105 is performed. The lithium aqueous solution after the calcium removal step S104 contains elemental 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 elemental Li contained in the lithium aqueous solution into a solid component containing elemental Li (hereinafter also referred to as a "lithium-containing solid component") and recover the elemental Li from the lithium aqueous solution. When a water-soluble carbonate is used for this purpose, a water-soluble carbonate having a solubility in water of 22.0 g / 100 g or more at the liquid temperature at which the recovery step S105 is performed is preferably used. Examples of such water-soluble carbonates include sodium carbonate. One type of water-soluble carbonate can be used alone, or two or more types can be used in combination. As the water-soluble carbonate used in this recovery step, sodium carbonate is particularly preferred from the viewpoints of ease of handling and low risk of becoming a new impurity source. When sodium carbonate is used as the water-soluble carbonate, a solid component containing lithium carbonate is generated in the lithium aqueous solution.

[0027] The amount of water-soluble carbonate added to the lithium aqueous solution is preferably within a predetermined range. Specifically, from the viewpoint of reliably producing 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 mol or more per mol of Li element in the lithium aqueous solution. Furthermore, from the viewpoint of recovering Li element with high purity, the amount of carbonate ions in the water-soluble carbonate is preferably 1.0 mol or less, more preferably 0.8 mol or less, and even more preferably 0.6 mol or less per mol of Li element in the lithium aqueous solution.

[0028] On the other hand, when carbon dioxide gas is used, the amount of carbon dioxide gas bubbled into the aqueous lithium solution is preferably an amount sufficient to convert the Li element contained in the aqueous lithium solution into a lithium-containing solid component.

[0029] When adding a water-soluble carbonate or carbon dioxide gas to the lithium aqueous solution, it is preferable to adjust the temperature of the lithium aqueous solution. This allows for efficient production of a lithium-containing solid component in the lithium aqueous solution. From this viewpoint, it is preferable to adjust the temperature of the lithium aqueous solution to, for example, 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. From the same viewpoint, it is also preferable to adjust the temperature of the lithium aqueous solution to, for example, 90°C or lower, more preferably 85°C or lower, and even more preferably 80°C or lower.

[0030] The lithium-containing solid component generated in the lithium aqueous solution in the recovery step S105 can be recovered by solid-liquid separation, for example, by filtering the lithium aqueous solution. In this way, the lithium-containing solid component is concentrated from the lithium aqueous solution. The liquid component obtained by separating the solid component from the lithium aqueous solution in the recovery step S105 contains, for example, halide ions contained in the lithium aqueous solution prepared in the dissolving step S101, halide ions derived from the acid used in the desulfurization step S102, and sodium ions derived from the water-soluble carbonate used in the recovery step S105.

[0031] Next, in the washing step S106, the lithium-containing solid component is washed with an aqueous liquid. In the washing step S106, the lithium-containing solid component is brought into contact with the aqueous liquid. The type of aqueous liquid is as described above. Upon contact, impurities contained in the lithium-containing solid component are dissolved in the aqueous liquid. The impurities referred to here include, for example, the halide ions and sodium ions described above. The aqueous liquid containing the impurities is recovered as a washing waste liquid. This step allows the impurities remaining in the lithium-containing solid component to be removed from the lithium-containing solid component, and the Li element to be recovered with high purity. Details of the aqueous liquid used in the washing step S106 will be described later.

[0032] The washing method for the lithium-containing solid component is not particularly limited, and any known method can be employed. From the viewpoint of balancing the ease of the washing method with high washing power, it is preferable to perform repulp washing or washing in a filtration device in the washing step S106. When performing repulp washing, the lithium-containing solid component recovered in the recovery step S105 is introduced into an aqueous liquid to form a slurry, which is then washed, making it easier for the aqueous liquid to permeate the lithium-containing solid component. This allows the entire lithium-containing solid component to be effectively washed. The inside of the filtration device can be washed, for example, by placing the lithium-containing solid component recovered in the recovery step S105 in a filtration device with a discharge function, passing the aqueous liquid through the filtration device to wash the cake, and then discharging the aqueous liquid from the filtration device using the discharge function after washing. This method is preferable because the washing process is completed simply by passing the aqueous liquid through the filtration device, eliminating the need for additional equipment such as a repulp tank. Whether repulp washing or washing in a filtration device is employed, the lithium-containing solid component can be effectively washed. From the viewpoint of further reducing the amount of impurities in the lithium-containing solid component, it is preferable to employ repulp washing.

[0033] In the washing step S106, from the viewpoint of recovering Li element with high purity, washing is preferably performed using an aqueous liquid adjusted to a predetermined temperature. Specifically, the temperature of the aqueous liquid during washing is preferably adjusted to 55° C. or higher, more preferably adjusted to 60° C. or higher, and even more preferably adjusted to 65° C. or higher. From the same viewpoint, the temperature of the aqueous liquid during washing is preferably adjusted to 80° C. or lower, and more preferably adjusted to 75° C. or lower.

[0034] The lithium-containing solid component is preferably washed thoroughly until the concentration of impurities in the washing wastewater generated in the washing step is below a predetermined value. Whether the concentration is below a predetermined value can be determined by measuring the concentration of impurities in the washing wastewater in the impurity concentration determination step S107 after washing the lithium-containing solid component. In the impurity concentration determination step S107, for example, halide ions and / or sodium ions are measured. In the present invention, impurities other than halide ions and sodium ions are sufficiently removed from the lithium aqueous solution by going through each step up to the recovery step S105. Therefore, by employing halide ions and / or sodium ions as the measurement targets, it is possible to determine that the lithium-containing solid component contains few impurities, i.e., that elemental lithium is concentrated in the lithium-containing solid component, based on the result that the total concentration of both ions is below a predetermined value. Alternatively, it is also possible to determine that elemental lithium 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.

[0035] The concentrations of halide ions and sodium ions in the cleaning wastewater can be measured, for example, by the following methods. Specifically, the concentration of halide ions can be measured using inductively coupled plasma atomic emission spectrometry (ICP-AES) or ion chromatography. The concentration of sodium ions can be measured using atomic absorption spectrometry or ICP-AES. Alternatively, qualitative concentration fluctuations of halide ions and sodium ions can be confirmed using an ion electrode method.

[0036] In the present invention, washing is preferably carried out until the total concentration of halide ions and sodium ions in the washing waste liquid is, for example, 0.100 g / L or less, more preferably 0.070 g / L or less, even more preferably 0.030 g / L or less, and still more preferably 0.010 g / L or less. The lower the total concentration of halide ions and sodium ions in the washing waste liquid, the better, but it may be, for example, 0.005 g / L or more.

[0037] The concentration of halide ions in the cleaning waste liquid is, for example, 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. The lower the concentration of halide ions in the cleaning waste liquid, the more preferable it is, but it may be, for example, 0.001 g / L or more. When two or more types of halide ions are contained in the cleaning waste liquid, the "concentration of halide ions in the cleaning waste liquid" refers to the total concentration of halide ions contained in the cleaning waste liquid.

[0038] The concentration of sodium ions in the washing waste liquid is, for example, 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 washing waste liquid, the better, but it may be, for example, 0.001 g / L or more.

[0039] In the impurity concentration determination step S107, if the measured concentration is equal to or less than the aforementioned value, it is determined that a lithium-containing solid component enriched in Li element has been recovered (purified product recovery step S108), and the method of the present invention can be terminated. In the purified product recovery step S108, the lithium-containing solid component is recovered, and the washing waste liquid generated by washing is also recovered. This washing waste liquid can be used in the washing waste liquid utilization step S109 described below. On the other hand, 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 washing step S106, where the lithium-containing solid component can be washed again. The washing 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 equal to or less than the aforementioned value. When the washing step S106 is performed multiple times, the time for washing the lithium-containing solid component may be changed each time.

[0040] When the cleaning step S106 is repeatedly performed, this step S106 can be configured to include n stages, from the first cleaning step to the n-th cleaning step. n is a natural number of 2 or more. From the viewpoint of keeping the total concentration of halide ions and sodium ions in the cleaning waste liquid at a predetermined value or less 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 more likely it is to pass the judgment in the impurity concentration judgment step S107, but it may be 5 or less.

[0041] The method of the present invention is characterized by including a step of washing a lithium-containing solid component and a step of utilizing the washing waste liquid. When recovering elemental Li from waste lithium solid-state batteries or non-standard materials, the purity of the elemental Li is required to be at a certain level or higher in order to reuse the elemental Li as a raw material for a solid electrolyte. Although a method for recovering elemental Li has been reported in Patent Document 1, the method described therein suffers from the problem that the recovered elemental Li is not sufficiently concentrated, resulting in the failure to obtain elemental Li with a purity suitable for reuse. In contrast, as described above, the method of the present invention, which includes a step of washing the lithium-containing solid component with an aqueous liquid, can increase the purity of elemental Li in the lithium-containing solid component and recover high-purity elemental Li suitable for reuse as a raw material for a solid electrolyte. Furthermore, as described below, the method of the present invention includes a washing waste liquid utilization step S109 utilizing the washing waste liquid generated in the washing step. This allows elemental Li unintentionally released into the washing waste liquid to be recovered, resulting in a higher yield of elemental Li.

[0042] In the cleaning waste liquid utilization step S109, the concentration of impurities in the cleaning waste liquid is first measured. The measurement targets are, for example, halide ions and / or sodium ions, as in the impurity concentration determination step S107. If the cleaning waste liquid contains excessive impurities, the impurities may circulate through the steps of the present invention, resulting in unintended accumulation of the impurities in the lithium-containing solid component. Therefore, measuring the concentration of impurities in the cleaning waste liquid and selectively utilizing cleaning waste liquid whose concentration is below a predetermined value is preferable from the perspective of recovering Li element with a high yield. For this reason, the total concentration of halide ions and sodium ions in the cleaning waste liquid generated in the cleaning waste liquid 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. Among these, when the cleaning waste liquid is used in the final cleaning step S106, the total concentration of halide ions and sodium ions in the cleaning waste liquid is particularly preferably, for example, 0.1 g / L or less.

[0043] Once it has been confirmed that the concentration of impurities in the cleaning waste liquid is below a predetermined value, the cleaning waste liquid can be reused in a process prior to the cleaning waste liquid utilization process S109. The method of the present invention may include multiple processes for removing impurities that may be contained in the lithium aqueous solution and the lithium-containing solid component. The cleaning process S106, in which the cleaning waste liquid is generated, is located downstream of the impurity removal process. Therefore, determining the process for utilizing the cleaning waste liquid as described above is preferable from the viewpoint of preventing the impurities contained in the cleaning waste liquid from inhibiting the concentration of Li element in the lithium-containing solid component. Furthermore, it is also preferable that the use of the cleaning waste liquid allows for the recovery of Li element that has unintentionally leaked into the cleaning waste liquid. If the concentration of impurities in the cleaning waste liquid exceeds a predetermined value, the cleaning waste liquid may be discarded without being returned to the system (disposal process S110).

[0044] The cleaning waste liquid utilization step S109 utilizing the cleaning waste liquid will be described below using an example in which the cleaning step comprises n stages. As described above, when the cleaning step S106 comprises the first to n-th cleaning steps, the cleaning waste liquid generated in the first cleaning step can be used as the aqueous liquid to be mixed with the lithium-containing compound in the dissolving step S101. By using the cleaning waste liquid in the dissolving step S101, Li element unintentionally leaked into the cleaning waste liquid can be recovered during the series of steps from step S101 to the purified product recovery step S108.

[0045] The cleaning waste liquid that can be used in the dissolving 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 pth cleaning step can also be used as the aqueous liquid to be mixed with the lithium-containing compound in the dissolving step S101. p is a natural number of 2 or more and n or less. The value of p can take any value, provided that it satisfies the relationship with the value of n. The process that uses the cleaning waste liquid is not limited to the dissolving step S101. For example, the cleaning waste liquid generated in the pth cleaning step can be used in the (p-m)th cleaning step S106, which is a cleaning step for cleaning the lithium-containing solid component. m is a natural number of 1 or more 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 step S106 in addition to the dissolving step S101, Li element that has unintentionally leaked into the cleaning waste liquid can be more effectively recovered. For these reasons, in the method of the present invention, the washing waste liquid generated in the pth washing step may be used as the aqueous liquid to be mixed with the lithium-containing compound in the dissolving step S101, or may be used to wash the lithium-containing solid component in the (pm)th washing step S106. Either case is preferable because it is possible to prevent the Li element from unintentionally leaking out of each step of the method of the present invention and to effectively recover the Li element.

[0046] In this way, a lithium-containing solid component, i.e., a solid component containing Li element, is recovered with high purity. The obtained solid component can be used as a solid electrolyte itself or as one of the raw materials for a solid electrolyte, either as it is or after being converted into a halide such as lithium chloride or lithium bromide or a sulfide such as lithium sulfide.

[0047] Although the present invention has been described above based on the preferred embodiments, the present invention is not limited to the above embodiments.

[0048] In relation to the above-described embodiments, the following lithium recovery method, lithium-containing solid component manufacturing method, and lithium element recovery method are further disclosed: [1] A lithium recovery method comprising: a dissolving step of mixing a compound containing lithium (Li) element with an aqueous liquid to obtain an aqueous lithium solution; a recovery step of recovering a solid component containing lithium (Li) element from the aqueous lithium solution; and a washing step of washing the solid component with the aqueous liquid.

[0049] [2] The method for recovering lithium according to [1], wherein the washing step consists of n stages, from a first washing step to an n-th washing step (n is a natural number of 2 or more). [3] The method for recovering lithium according to [2], wherein the washing waste liquid generated in the first washing step is used as the aqueous liquid to be mixed with the compound in the dissolving step. [4] The method for recovering lithium according to [2] or [3], wherein the washing waste liquid generated in the p-th washing step is used as the aqueous liquid to be mixed with the compound in the dissolving step, or is used to wash the solid component in the (p-m)th washing step (p is a natural number of 2 or more and n or less, and m is a natural number of 1 or more and less than p). [5] The method for recovering lithium according to any one of [1] to [4], wherein the washing step is a repulping washing step or a step of washing in a filtration device. [6] The method for recovering lithium according to any one of [1] to [5], wherein washing is carried out until the total concentration of halide ions and sodium ions in the washing wastewater generated in the washing step is 0.100 g / L or less.

[0050] [7] The method for recovering lithium according to any one of [1] to [6], wherein the compound further contains phosphorus (P). [8] The method for recovering lithium according to [7], wherein, after the dissolving step, a phosphorus removal step of adding calcium carbonate to the lithium aqueous solution to remove from the lithium aqueous solution a solid component containing calcium phosphate formed in the lithium aqueous solution, and a calcium removal step of adjusting the pH of the lithium aqueous solution to remove from the lithium aqueous solution a solid component containing calcium formed in the lithium aqueous solution, and the recovering step is performed after the calcium removal step. [9] The method for recovering lithium according to any one of [1] to [8], wherein the recovering step is a step of adding a water-soluble carbonate to the lithium aqueous solution to recover from the lithium aqueous solution a solid component containing lithium carbonate formed in the lithium aqueous solution.

[10] A method for producing a solid component containing lithium, comprising: a dissolving step of mixing a compound containing lithium (Li) with an aqueous liquid to obtain a lithium aqueous solution; a recovering step of recovering a solid component containing lithium (Li) from the lithium aqueous solution; and a washing step of washing the solid component with an aqueous liquid.

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

[0051] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, "%" means "% by mass."

[0052] [Example 1] (1) Dissolving step S101 Li ５．４ P.S. ４．４ Cl ０．４ Br ０．６ 10.0 g of the above was mixed with 100 mL of a 0.14 mol / L aqueous lithium carbonate solution simulating the washing waste liquid to prepare an aqueous lithium solution.

[0053] (2) Desulfurization step S102 15 mL of 12 mol / L hydrochloric acid was added to the lithium aqueous solution to adjust the pH of the lithium aqueous solution to be equal to or less than 1. Next, the lithium aqueous solution was adjusted to 70° C. to generate hydrogen sulfide, and the S element was removed from the liquid.

[0054] (3) Phosphorus Removal Step S103: 0.12 mol of calcium carbonate was added to the lithium aqueous solution to cause calcium phosphate precipitation in the lithium aqueous solution. The precipitated calcium phosphate was removed from the lithium aqueous solution using a Nutsche filter.

[0055] (4) Calcium Removal Step S104: 0.2 mol of solid sodium hydroxide was added to the lithium aqueous solution to adjust the pH of the lithium aqueous solution to 10.0. This caused calcium hydroxide to precipitate in the lithium aqueous solution. The precipitated calcium hydroxide was removed from the lithium aqueous solution using a Nutsche filter.

[0056] (5) Recovery step S105: 0.14 mol of sodium carbonate was added to an aqueous lithium solution adjusted to 70° C. to cause precipitation of lithium carbonate in the aqueous lithium solution. The precipitated lithium carbonate was recovered from the aqueous lithium solution using a Nutsche filter.

[0057] (6) Washing Step S106 The lithium carbonate was repulp washed with 100 mL of a saturated aqueous solution of lithium carbonate at a liquid temperature of 70°C.

[0058] (7) Impurity Concentration Determination Step S107: A portion of the cleaning waste liquid generated in the cleaning step S106 was recovered, and the chloride ion concentration, bromide ion concentration, and sodium ion concentration in the cleaning waste liquid were measured. The measurements were performed using an ICP-AES analyzer (model: SPS3500DD) manufactured by Hitachi High-Tech Science Corporation, using a calibration curve method. The measurement results are shown in Table 1 below.

[0059] (8) Purified Product Recovery Step S108 The lithium carbonate washed in the washing step S106 was recovered using a Nutsche filter.

[0060] [Example 2] The dissolving step S101 to the recovery step S105 were carried out in the same manner as in Example 1. In the washing step S106, repulp washing of the lithium carbonate was carried out 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 was used in both washing stages. Subsequently, the impurity concentration determination step S107 and the purified product recovery step S108 were carried out in the same manner as in Example 1, and lithium carbonate was obtained.

[0061] [Example 3] The dissolving step S101 to the recovery step S105 were carried out in the same manner as in Example 1. In the washing step S106, repulp washing of the lithium carbonate was carried out 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 was used in all three washing stages. Subsequently, the impurity concentration determination step S107 and the purified product recovery step S108 were carried out in the same manner as in Example 1, and lithium carbonate was obtained.

[0062]

[0063] As is clear from the results shown in Table 1, it can be seen that washing lithium carbonate reduces the concentrations of chloride ions, bromide ions, and sodium ions in the washing waste liquid. A low concentration of these ions in the washing waste liquid means that the purity of the obtained lithium carbonate is high. Therefore, it can be seen that washing lithium carbonate increases the purity of the lithium carbonate. It can also be seen that repeating the washing process further increases the purity of the lithium carbonate.

[0064] According to the present invention, a method is provided that can recover lithium element with high purity from a lithium-containing compound.

Claims

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

2. The method for recovering lithium according to claim 1, wherein the washing step comprises n steps, from a first washing step to an n-th washing step (n is a natural number of 2 or more).

3. The method for recovering lithium according to claim 2, wherein a washing waste liquid generated in the first washing step is used as the aqueous liquid to be mixed with the compound in the dissolving step.

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

5. The method for recovering lithium according to claim 1, wherein the washing step is a repulping step or a washing step in a filtration device.

6. The method for recovering lithium according to claim 1, wherein washing is carried out until the total concentration of halide ions and sodium ions in the washing waste liquid generated in the washing step becomes 0.100 g / L or less.

7. The method for recovering lithium according to claim 1, wherein the compound further contains phosphorus (P).

8. The method for recovering lithium according to claim 7, further comprising the steps of: after the dissolving step, performing a phosphorus removal step of adding calcium carbonate to the lithium aqueous solution to remove from the lithium aqueous solution a solid component containing calcium phosphate formed in the lithium aqueous solution; and after the phosphorus removal step, performing a calcium removal step of adjusting the pH of the lithium aqueous solution to remove from the lithium aqueous solution a solid component containing calcium formed in the lithium aqueous solution; and performing the recovering step after the calcium removal step.

9. The method for recovering lithium according to claim 1, wherein the recovery step is a step of adding a water-soluble carbonate to the aqueous lithium solution to produce a solid component containing lithium carbonate in the aqueous lithium solution, and recovering the solid component from the aqueous lithium solution.

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

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

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