How to manufacture lithium hydroxide

Abstract

To provide a method for efficiently producing high-purity lithium hydroxide with lower energy.SOLUTION: A method for producing lithium hydroxide from a lithium ion extract extracted from a treatment member of a lithium secondary battery by recovering only Li ions into a recovery liquid by using a Li permselective membrane, comprises: recovering the recovery liquid while adjusting a temperature of the recovery liquid to 50°C or higher; and separating the lithium hydroxide from the recovery liquid.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing lithium hydroxide. [Background technology]

[0002] With the recent rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as their power sources has become increasingly important. Conventionally, batteries used for such applications have used electrolytes containing flammable organic solvents, but by making batteries all-solid-state, flammable organic solvents are not used in the battery, safety devices can be simplified, and manufacturing costs and productivity can be improved. Therefore, batteries in which the electrolyte is replaced with a solid electrolyte layer are being developed.

[0003] Lithium secondary batteries and the like are used as batteries for the above-mentioned applications, and in recent years, their use in hybrid cars and electric vehicles, which are being developed to comply with carbon dioxide emission regulations, has also been considered. As a result, securing lithium sources has become more urgent than ever, and as part of this, technologies for recovering lithium by recycling lithium secondary batteries have been developed (see, for example, Patent Document 1).

[0004] Sulfide solid electrolytes are known as solid electrolytes used in lithium secondary batteries and the like. Sulfide solid electrolytes have high ionic conductivity and are therefore useful for increasing the output of batteries. Lithium sulfide is widely used as a raw material for producing sulfide solid electrolytes, and there is increasing demand for lithium hydroxide, which is a raw material for lithium sulfide. One method for producing lithium hydroxide is to electrolyze an aqueous lithium carbonate solution or suspension and pass the electrolysis through an ion exchange membrane to produce an aqueous lithium hydroxide solution (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-81953 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-270188 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology described in Patent Document 1 uses a lithium ion conductor to recover lithium ions from a source solution containing lithium ions, but with the increasing demand for lithium, there is an ever-increasing demand for improved lithium recovery efficiency. Furthermore, the technology described in Patent Document 2 is limited to lithium carbonate as the raw material for lithium hydroxide, and further improvements are required to obtain lithium hydroxide from other lithium-containing aqueous solutions and other raw materials. Furthermore, obtaining lithium hydroxide using the technology described in Patent Document 2 and other methods requires a dehydration step, such as heating and concentration, which consumes a lot of energy. Therefore, reducing this energy consumption is necessary to obtain lithium more cheaply.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for efficiently producing high-purity lithium hydroxide with less energy and an apparatus for producing lithium hydroxide. [Means for solving the problem]

[0008] As a result of extensive research into solving the above problems, the present inventors have found that the problems can be solved by the following invention.

[0009] 1. A method for producing lithium hydroxide from a lithium ion extract solution extracted from a processing component of a lithium secondary battery, by using a Li permselective membrane to recover only Li ions into a recovery solution, The temperature of the recovered liquid is adjusted to 50°C or higher while the recovered liquid is recovered; and separating lithium hydroxide from the recovered solution; A method for producing lithium hydroxide, comprising: 2. The method for producing lithium hydroxide according to the above item 1, wherein the temperature is 80°C or higher and 100°C or lower. 3. The method for producing lithium hydroxide according to 1 or 2 above, wherein the separation is carried out by crystallization. 4. The method for producing lithium hydroxide according to 3 above, wherein the crystallization is cooling crystallization. 5. The method for producing lithium hydroxide according to 4 above, wherein the cooling and crystallization is carried out while maintaining a positive pressure by blowing an inert gas into the recovered liquid to be subjected to the crystallization. 6. The method for producing lithium hydroxide according to 4 or 5 above, wherein the cooling crystallization is carried out while adjusting the temperature of the recovered liquid to be subjected to the crystallization to 40°C or less. 7. The method for producing lithium hydroxide according to 3 above, wherein the crystallization is evaporative crystallization. 8. The method for producing lithium hydroxide according to 7 above, which comprises adding pure water produced by the evaporation and crystallization to the filtrate or the recovered liquid. 9. The method for producing lithium hydroxide according to any one of the above items 3 to 8, further comprising adding a filtrate produced by the crystallization to the recovered liquid. 10. The method for producing lithium hydroxide according to claim 9, wherein the filtrate is heated. 11. The method for producing lithium hydroxide according to claim 10, wherein the heating utilizes waste heat or excess heat from the crystallization. 12. The method for producing lithium hydroxide according to any one of 9 to 11 above, wherein impurities are not removed when the filtrate is added to the recovered liquid. 13. The method for producing lithium hydroxide according to any one of 1 to 12 above, wherein the Li permselective membrane contains an oxide or oxynitride containing Li. 14. A Li-ion recovery tank equipped with a Li-permselective membrane that recovers only Li ions from a lithium ion extract extracted from a processing component of a lithium secondary battery; a recovery liquid storage tank for storing a recovery liquid for recovering the Li ions; a temperature adjusting means for adjusting the temperature of the recovery liquid to 50°C or higher; and a separation device for separating lithium hydroxide from the recovered solution; A lithium hydroxide manufacturing apparatus comprising: 15. The lithium hydroxide manufacturing apparatus according to claim 14, wherein the separation device is a crystallization device. 16. The lithium hydroxide manufacturing apparatus according to claim 15, further comprising a filtrate recovery means for adding the filtrate produced in the crystallizer to the recovery liquid. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method and an apparatus for producing high-purity lithium hydroxide efficiently using less energy. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a flow diagram showing one embodiment of an apparatus for producing lithium hydroxide capable of carrying out the method for producing lithium hydroxide of the present embodiment. [Figure 2] FIG. 1 is a flow diagram showing one embodiment of an apparatus for producing lithium hydroxide capable of carrying out the method for producing lithium hydroxide of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a method for producing lithium hydroxide and an apparatus for producing lithium hydroxide according to one embodiment of the present invention (hereinafter referred to as "this embodiment") will be described. Note that the method for producing lithium hydroxide and the apparatus for producing lithium hydroxide according to one embodiment of the present invention are merely one embodiment of the method for producing lithium hydroxide and the apparatus for producing lithium hydroxide according to one embodiment of the present invention, and the present invention is not limited to the method for producing lithium hydroxide and the apparatus for producing lithium hydroxide according to one embodiment of the present invention. Furthermore, in this specification, lithium means both lithium and lithium ions, and should be interpreted appropriately unless technical contradiction arises.

[0013] [Method of manufacturing lithium hydroxide] The lithium hydroxide production method of this embodiment involves recovering only Li ions from a source solution containing an aqueous Li ion solution, particularly a lithium ion extract extracted from processing components of a lithium secondary battery, into a recovery solution using a Li permselective membrane, and then producing lithium hydroxide from the recovery solution. This method is characterized by comprising recovering the Li ions while controlling the temperature of the recovery solution to 50°C or higher, and separating lithium hydroxide from the recovery solution. In this production method, adjusting the recovery solution to a specific temperature condition of 50°C or higher increases the Li ion solubility in the recovery solution, thereby enabling the recovery of large amounts of Li ions. Furthermore, by crystallizing the heated recovery solution, lithium hydroxide can be produced while reducing energy consumption. Furthermore, the use of a Li permselective membrane eliminates the need for specific types of source solution, allowing for the use of a wide range of source solutions, as long as they contain an aqueous Li ion solution. However, in this embodiment, a lithium ion extract extracted from processing components of a lithium secondary battery is used. Thus, this production method enables the production of high-purity lithium hydroxide efficiently and with less energy.

[0014] [Only Li ions are recovered in the recovery liquid] The method for producing lithium hydroxide according to this embodiment involves recovering only Li ions from a lithium ion extract (sometimes simply referred to as "stock solution") extracted from a processing component of a lithium secondary battery, which serves as a stock solution containing an aqueous Li solution, into a recovery solution using a Li permselective membrane. Here, "Li ions only" means that the extract contains substantially no ions other than Li ions, and the content of the other ions is 0.5% by mass or less.

[0015] (Undiluted) The source solution containing the Li ion aqueous solution can be any solution containing Li ions without any particular limitations, and examples thereof include concentrated water obtained by concentrating seawater, salt lake brine, mining wastewater, geothermal water, or a combination of these by means of evaporation or the like. The stock solution may also be the above-mentioned stock solution, i.e., a Li-ion extract extracted from a processing component of a lithium secondary battery. The Li-ion extract is not particularly limited as long as it is extracted from a processing component, but examples include a Li-ion extract extracted from a processing component of a lithium secondary battery containing a sulfide-based solid electrolyte, i.e., a Li-ion extract containing a sulfide-based solid electrolyte. In this embodiment, the above-mentioned seawater or Li-ion extract may be used alone or in combination.

[0016] In this embodiment, the sulfide-based solid electrolyte refers to a solid electrolyte containing at least lithium and sulfur. Representative examples include those containing lithium, sulfur, and phosphorus, such as Li2S-P2S5, and further containing halogen elements, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-LiI-LiBr, Li2S-P2S5-Li2O-LiI, and Li2S-SiS2-P2S5-LiI.

[0017] Regarding the Li ion extract, a typical example of the Li ion extract extracted from the processing component of a lithium secondary battery containing a sulfide-based solid electrolyte is an aqueous solution of a sulfide-based solid electrolyte obtained by dissolving the sulfide-based solid electrolyte used in the lithium secondary battery in an alkaline aqueous solution.

[0018] Preferred examples of the alkaline component of the alkaline aqueous solution for dissolving the sulfide-based solid electrolyte include sodium hydroxide, lithium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, calcium hydroxide, barium hydroxide, europium(II) hydroxide, thallium(I) hydroxide, and guanidine. These alkaline components may be used alone or in combination of two or more. From the viewpoint of ease of dissolving the sulfide-based solid electrolyte, sodium hydroxide, potassium hydroxide, and calcium hydroxide are more preferred as the alkaline component.

[0019] The Li ion extract used as the stock solution can be prepared using a commonly known electrodialysis device. + ), Na ions (Na + ) and other monovalent cations pass through the cation exchange membrane and move to the cathode (treatment solution), while other polyvalent cations have difficulty passing through the cation exchange membrane, and negative ions do not pass through the cation exchange membrane. + ) moves from the raw material liquid into the treatment liquid. At the cathode, OH is produced by the electrolysis of water. - Therefore, by using an electrodialysis device, Li ions in the raw material solution can be transferred to the treated solution, and at the same time, the treated solution can be made alkaline. However, in this electrodialysis treatment, other monovalent positive ions, Na ions (Na + ) and other (non-Li monovalent positive ions) also migrate into the treated solution at the same time. Therefore, by using the treated solution after electrodialysis as the raw solution, Li ions can be selectively recovered in the recovered solution.

[0020] That is, when the Li ion extract is non-alkaline, an alkaline aqueous solution (treated solution) containing Li ions can be produced using a commonly known, general electrodialysis device, and by using this as the raw solution, Li (Li ions) can be obtained in the recovered solution with high efficiency.

[0021] (Recovered liquid) The recovery liquid used in this embodiment is not particularly limited as long as it can dissolve Li ions, and can be appropriately selected depending on the form of lithium to be finally obtained. For example, the recovery liquid preferably used is pure water such as distilled water or ion-exchanged water. In the manufacturing method of this embodiment, the recovery liquid is supplied as water such as pure water or ion-exchanged water, and by transferring Li ions from the source liquid and recovering the Li ions, a recovery liquid containing Li ions (hereinafter, may be simply referred to as a "Li-ion-containing recovery liquid") is obtained. After lithium hydroxide is crystallized from the Li-ion-containing recovery liquid, the recovery liquid becomes substantially free of Li ions. The recovery liquid substantially free of Li ions produced by crystallization is also referred to as a filtrate. The filtrate is obtained by removing Li ions from the Li-ion-containing recovery liquid through crystallization, and can be said to be a recovery liquid substantially free of Li ions.

[0022] (Adjusting the temperature of the recovered liquid) In this embodiment, in order to recover only Li ions from the raw solution into the recovery solution, it is necessary to adjust the temperature of the recovery solution to 50° C. or higher. If the temperature of the recovery solution is lower than 50° C., Li ions cannot be recovered into the recovery solution with high efficiency, and the efficiency of crystallization of lithium hydroxide from the recovery solution also decreases. When Li ions are recovered while maintaining the temperature of the recovery solution at 50°C or higher, Li ions can be recovered with high efficiency. In other words, by maintaining the temperature at 50°C or higher, the solubility of lithium ions in the recovery solution increases, and the increased amount of lithium ions is supplied from the raw solution, allowing for the recovery of large amounts of lithium ions. Furthermore, by crystallizing the heated recovery solution, it is possible to produce lithium hydroxide while reducing energy consumption.

[0023] In this embodiment, the temperature of the recovery liquid adjusted in recovering Li ions is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher, with the upper limit being preferably 100°C or lower, more preferably 95°C or lower, and even more preferably 90°C or lower. Note that the temperature of the recovery liquid in this specification refers to the set value of the temperature to be adjusted, and since the actual temperature of the recovery liquid may fluctuate above or below the set value, the actual temperature of the recovery liquid includes a range of less than ±2.0°C. The same applies to the temperature of the raw liquid described below.

[0024] In this embodiment, the pH of the stock solution may be controlled. By controlling the pH, Li can be efficiently recovered. In this case, it is preferable to adjust the pH to a range of 12 to 14. Note that a pH of 12 to 14 is an adjustment target. In this embodiment, a pH of 12 to 14 includes a value of 11.5 to less than 12.5, and a pH of 14 includes a value of 13.5 to less than 14.5, and essentially means a range of 11.5 to less than 14.5.

[0025] In this embodiment, the pH of the raw solution may be controlled by any method, for example, by adding an alkaline aqueous solution to the raw solution. The pH of the raw solution may be controlled when recovering Li ions into the recovery solution, i.e., the pH of the raw solution may be controlled while recovering Li ions into the recovery solution, or may be controlled in advance before recovering Li ions into the recovery solution.

[0026] Preferred examples of alkaline components of the alkaline aqueous solution used to adjust the pH of the stock solution include sodium hydroxide, lithium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, calcium hydroxide, barium hydroxide, europium(II) hydroxide, thallium(I) hydroxide, and guanidine. These alkaline components may be used alone or in combination of two or more. Among these, sodium hydroxide is more preferred from the viewpoint of being able to quickly adjust the pH of the lithium ion extract.

[0027] The temperature of the raw solution may be adjusted, specifically, heated, in the same manner as the recovery solution. This makes it easier to adjust the temperature of the recovery solution to 50°C or higher, enabling highly efficient recovery of Li ions. When adjusting the temperature of the raw solution, the adjustment temperature may be set within the adjustment range of the temperature of the recovery solution.

[0028] (Li selective permeable membrane) The Li permselective membrane is a membrane that has the function of transferring Li ions in the raw solution to the recovered solution, and is usually provided so as to separate the raw solution from the recovered solution. The Li-permselective membrane is preferably composed of a Li-permselective membrane body made of a super Li-ion conductor (ion conductor) with particularly high ionic conductivity, and a Li-adsorption layer formed as a thin layer on the source liquid side. Using a super Li-ion conductor as the Li-permselective membrane body can increase the ionic current of Li ions flowing between the electrodes, thereby improving the Li recovery efficiency. Here, the Li ions contained in the aqueous solution exist as Li hydrated ions, with water molecules coordinating around them. Therefore, in order to further increase the ionic current, it is effective to create a condition where water molecules can be easily removed from the surface of the Li-permselective membrane (the interface between the Li-permselective membrane and the raw solution). For this reason, it is preferable that a Li adsorption layer that adsorbs Li ions (excluding hydrates) in the Li ion extract is formed on the surface of the Li permselective membrane. That is, it is preferable that the Li permselective membrane is one that has been subjected to a surface Li adsorption treatment. As the Li adsorption layer, as will be described later, one that is formed by modifying the surface of the material that constitutes the Li permselective membrane is preferred.

[0029] Preferred materials for the Li permselective membrane body include, for example, the following oxides, oxynitrides, etc. containing Li. That is, the Li permselective membrane preferably contains the following oxides, oxynitrides, etc. containing Li. Examples of oxides containing Li include lithium lanthanum titanate (Li x ,La y )TiO z (where x=3a-2b, y=2 / 3-a, z=3-b, 0<a≦1 / 6、0≦b≦0.06、x> 0) (hereinafter also referred to as "LLTO"), lithium lanthanum zirconate: Li7La3Zr2O 12 (hereinafter also referred to as "LLZO"), lithium lanthanum niobate: Li5La3Nb2O 12 , lithium lanthanum tantalate: Li5La3Ta2O 12The LLTO is more specifically Li 0.29 La 0.57 TiO3 (a≒0.1, b≒0) can be used.

[0030] These materials can be obtained as sintered bodies by mixing particles made of these materials with sintering aids and sintering the mixture at high temperatures (above 1000°C). In this case, the surface of the Li-permselective membrane can be configured as a porous structure in which fine particles made of LLTO are bonded (sintered), thereby increasing the effective surface area of ​​the Li-permselective membrane itself. This is true not only for LLTO, but also for other Li-containing oxides and oxynitrides, which will be described later.

[0031] As the super Li ion conductor that can be used as the material for constituting the Li permselective membrane body, in addition to the above-mentioned LLTO, LLZO, etc. as an oxide containing Li, for example, Li substituted NASICON (Na Super Ionic Conductor) type crystal, 1+x+y Al x (Ti,Ge) 2-x Si y P 3-y O 12 (where 0≦x≦0.6, 0≦y≦0.6) (Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2 system, hereinafter also referred to as "LASiPTiGeO") and the like are also included.

[0032] Preferred examples of oxynitrides containing Li include lithium phosphate oxynite (Li3PON, hereinafter also referred to as "LiPON"), nitride of LLTO (LLTON), nitride of LLZO (LLZON), nitride of LASiPTiGeO (LASiPTiGeON), and the like.

[0033] The above-mentioned super Li-ion conductors, such as oxides and oxynitrides containing Li, contain Li as one of their constituent elements, and exhibit ionic conductivity when Li ions outside the crystal move between Li sites in the crystal. Li ions flow through the Li-selective membrane itself, but sodium ions cannot flow within the Li-selective membrane. In this case, it is the Li ions (Li + ) and the Li hydrate ions present in the original solution along with the Li ions cannot enter the Li sites and therefore do not conduct through the crystal. In this respect, it is the same as the Li permselective membrane described in WO2015 / 020121.

[0034] Here, if a large amount of Li ions in particular are adsorbed onto the surface of the Li permselective membrane body by the Li adsorption layer, the water molecules of the Li hydrated ions are removed during adsorption, leaving only Li ions, thereby increasing the Li ion conduction efficiency (ionic current flowing through the Li permselective membrane body) from the raw liquid side (one main surface side) of the Li permselective membrane body to the recovered liquid side (the other main surface side).

[0035] The Li permselective membrane preferably has an anode and a cathode bonded thereto, with the anode bonded to the raw liquid side (one of the main surfaces) of the Li permselective membrane and the cathode bonded to the recovered liquid side (the other main surface). With this configuration, the one main surface of the Li permselective membrane on the raw liquid side and the other main surface on the recovered liquid side are maintained at a constant positive potential and a constant negative potential, respectively. The anode and cathode may be made of metal materials that do not undergo electrochemical reactions in the raw solution and recovered solution, such as SUS, Ti, and Ti-Ir alloys.

[0036] Although the above materials used as Li-permselective membranes are solids, they are known to exhibit conductivity due to the flow of Li ions within the crystals in a form similar to free electrons. Therefore, when the anode is at a positive potential and the cathode is at a negative potential, Li ions (positive ions) in the source solution on the anode side that reach the cathode side of the Li-permselective membrane will flow by ionic conduction from the anode side (source solution) of the Li-permselective membrane to the cathode side (recovered solution). Li ions that reach the cathode side of the Li-permselective membrane are recovered in the recovered solution. Therefore, after a certain time has passed, the Li-ion concentration in the source solution decreases, while the Li-ion concentration in the recovered solution increases.

[0037] The Li adsorption layer is formed as a thin layer on the surface of the Li permselective membrane body by chemically treating the Li permselective membrane body. Specifically, it is formed by acid treatment of one main surface of the Li permselective membrane body (for example, LLTO), for example by exposing this surface to hydrochloric acid or nitric acid for 5 days. By this treatment, Li, which is particularly susceptible to oxidation among the constituent elements of the Li permselective membrane body (for example, LLTO), is replaced with hydrogen in the acid, and the Li adsorption layer is formed as H 0.29 La 0.57 It is presumed that a layer of material (HLTO) with a composition similar to TiO3 is formed. The formation of a thin surface layer (HLTO) is supported by the X-ray diffraction results in WO2017 / 131051, which show peaks that are different from those of the Li permselective membrane itself (e.g., LLTO).

[0038] The H sites in HLTO were originally intended for Li, so H is particularly susceptible to substitution by Li ions, but is difficult to substitute by other ions (such as sodium ions). For this reason, HLTO functions as a Li adsorption layer. Furthermore, because HLTO is produced by a reaction with acid, it is only formed on the outermost surface of the Li permselective membrane itself.

[0039] [Separating lithium hydroxide] The method for producing lithium hydroxide according to this embodiment is a method for producing lithium hydroxide from a recovered solution, and includes separating lithium hydroxide from the recovered solution. Specifically, in the production method according to this embodiment, after recovering only Li ions in the recovered solution, lithium hydroxide is separated from a recovered solution containing Li ions (Li-ion-containing recovered solution) obtained by recovering only Li ions from the raw solution. This allows lithium hydroxide to be obtained without the need for a dehydration step such as heating and concentration, thereby reducing the energy consumption required for the dehydration step and making it possible to obtain a lithium source more efficiently. The separation method is not particularly limited as long as lithium hydroxide can be obtained from the Li ion-containing recovery solution, and preferred examples include crystallization methods such as cooling crystallization and evaporation crystallization.

[0040] (cooling crystallization) In cooling crystallization, the recovery liquid is heated in a stage prior to crystallization, thereby increasing the Li ion content in the recovery liquid and creating a temperature difference, thereby enabling more efficient recovery of Li ions. In the case of cooling crystallization, there are no particular limitations on the specific method used, as long as it is performed using a conventional cooling crystallization technique. For example, it is preferable to perform the crystallization by blowing an inert gas into the Li ion-containing recovery liquid while maintaining a positive pressure. Blowing in an inert gas can suppress the formation of lithium carbonate (hereinafter sometimes simply referred to as "carbonation"), further promoting the formation of lithium hydroxide by cooling crystallization, allowing for more efficient production of high-purity lithium hydroxide.

[0041] When the recovery liquid is heated in a stage prior to crystallization, the heating temperature is preferably 50° C. or higher, more preferably 60° C. or higher, with the upper limit being 80° C. or lower. When the heating temperature is within the above range, cooling crystallization can be carried out more efficiently.

[0042] There are no particular limitations on the positive pressure, and it is usually sufficient to set the pressure at about 0.1 to 30 kPa as a gauge pressure, and from the viewpoint of more efficient freeze crystallization, it is preferably 0.5 to 10 kPa. As the inert gas, nitrogen gas, argon gas, etc. may be used. The positive pressure may be achieved by adjusting the supply and exhaust of the inert gas so that cooling and crystallization are carried out under positive pressure. From the viewpoint of suppressing carbonation, a gas containing oxygen may be used as long as the concentration of carbon monoxide, carbon dioxide, or hydrocarbon is 10 ppm or less. To obtain lithium hydroxide with higher purity, a concentration of 1 ppm or less is preferred, and 0.1 ppm is more preferred.

[0043] In the case of cooling crystallization, it is preferable to carry out the crystallization while adjusting the temperature to 40° C. or less from the viewpoint of more efficient cooling crystallization. From the same viewpoint, the crystallization temperature is preferably 35° C. or less, more preferably 30° C. or less, and even more preferably 25° C. or less. There is no particular restriction on the lower limit, but it may be above 0° C., and is preferably 3° C. or more.

[0044] In the production method of this embodiment, when cooling crystallization is employed as the crystallization, cooling of the Li-ion-containing recovery solution may be included as necessary. By including cooling, the temperature of the Li-ion-containing recovery solution can be actively adjusted to the above-mentioned preferred temperature, making it possible to perform cooling crystallization more efficiently. Therefore, from the viewpoint of performing crystallization more efficiently, it is preferable to perform crystallization after cooling of the Li-ion-containing recovery solution. The method for cooling the Li-ion-containing recovery liquid may be either an air-cooling method or a water-cooling method, and a cooler appropriate for the method to be used may be used.

[0045] (evaporation crystallization) In evaporative crystallization, the recovered liquid is heated prior to crystallization, so the energy required for evaporation can be reduced. In the case of evaporative crystallization, the specific method is not particularly limited as long as it is carried out by a conventional evaporative crystallization technique, and for example, it is preferable to carry out the evaporative crystallization while adjusting the temperature preferably to 80°C or higher and 100°C or lower. From the viewpoint of more efficient evaporative crystallization, the adjusted temperature is more preferably 85°C or higher, and even more preferably 90°C or higher.

[0046] From the viewpoint of more efficient evaporation and crystallization, evaporation and crystallization is preferably carried out under a reduced pressure atmosphere. By reducing the pressure, water vapor generated in the system can be discharged and added to the filtrate or the recovered liquid for recovery.

[0047] When reducing the pressure, there are no particular limitations on the pressure, and the vacuum pressure is usually about 0.05 to 10 kPa, and from the viewpoint of more efficient evaporation and crystallization, it is preferably 0.1 to 5 kPa, more preferably 0.2 to 1 kPa. The evaporation and crystallization may be carried out while supplying an inert gas, such as nitrogen gas or argon gas. From the viewpoint of suppressing carbonation, the gas may contain oxygen as long as the concentration of carbon monoxide, carbon dioxide, or hydrocarbon is 10 ppm or less. To obtain lithium hydroxide with higher purity, the concentration is preferably 1 ppm or less, and more preferably 0.1 ppm.

[0048] [Add the filtrate to the recovered solution] The production method of this embodiment can include adding the filtrate produced by the crystallization to a recovery solution. The filtrate is added to replenish the water in the recovery solution in order to recover lithium ions from the recovery solution as lithium hydroxide anhydride or lithium hydroxide hydrate. By adding the filtrate to the recovery solution and reusing it, it is possible to reduce the amount of lithium discharged from the filtrate and the amount of discharge of the filtrate itself, which is a major advantage. Furthermore, the amount of new pure water used as the recovery solution can be reduced, allowing for more efficient production of lithium hydroxide. The recovery solution to which the filtrate is added is a recovery solution used to transfer Li ions from the raw solution, and is not a Li ion-containing recovery solution. In this embodiment, a heat exchanger can be further provided that can utilize the waste heat from cooling crystallization and the excess heat generated by evaporation crystallization to heat the recovered liquid, thereby further improving thermal efficiency.

[0049] As described above, in the case of evaporative crystallization, the pure water produced by evaporative crystallization can be easily reused by adding it to the filtrate or the recovered liquid, thereby reducing the amount of new pure water used. Furthermore, compared to the case of supplying new pure water, the filtrate may be reused at a higher temperature than the new pure water, making it possible to produce lithium hydroxide more efficiently in terms of thermal energy. Cooling crystallization also produces a filtrate. Because this filtrate is produced by crystallizing lithium hydroxide from a Li-ion-containing recovery solution, it can be considered a recovery solution from which Li ions have been removed and which is substantially free of Li ions. However, it may contain Li ions. In this case, the filtrate may not be pure water. However, it can be reused by adding it to the recovery solution, thereby reducing the amount of new pure water required and enabling more efficient production of lithium hydroxide. Thus, whether cooling crystallization or evaporation crystallization is used for crystallization, the filtrate produced by crystallization can be reused by adding it to the recovery solution. Generally, impurities contained in the solution to be crystallized remain in the filtrate discharged by crystallization. However, in the production method of this embodiment, the recovery solution to be crystallized contains only Li ions recovered through a Li-permselective membrane. Therefore, the filtrate discharged by crystallization contains only Li ions and no other impurities. Therefore, the reuse of the filtrate in this embodiment is possible precisely because of the use of a Li-permselective membrane.

[0050] When the filtrate is added to the recovery liquid, the filtrate may be heated as necessary. In the production method of this embodiment, the temperature of the recovery liquid is adjusted to 50°C or higher. However, by heating the filtrate and adding it to the recovery liquid, the temperature of the recovery liquid can be increased, promoting the migration of Li ions from the raw solution to the recovery liquid and facilitating the recovery of Li ions in the recovery liquid, thereby enabling more efficient production of lithium hydroxide. When the filtrate is heated, the temperature is preferably set to 50°C or higher, and more preferably, the temperature is set to the more preferable adjustment temperature of the recovery liquid. In addition, the filtrate can be heated using heat sources that can be used to heat the recovery liquid, such as exhaust heat from cooling crystallization and excess heat generated by evaporation crystallization.

[0051] Furthermore, when the filtrate is added to the recovery liquid, although the filtrate may contain Li ions as described above, impurities other than Li ions are removed by the selectively permeable membrane, and therefore the filtrate can be reused without any additional impurity removal.

[0052] The lithium hydroxide obtained by crystallization is usually a monohydrate (LiOH HO). In the production method of this embodiment, the lithium hydroxide is separated from the filtrate by solid-liquid separation or the like, and the obtained lithium hydroxide can be used as is or can be further dehydrated before use depending on the application. The lithium hydroxide monohydrate may be dehydrated by a conventional drying method such as heating or reducing pressure.

[0053] [Lithium hydroxide manufacturing equipment] The lithium hydroxide manufacturing apparatus of this embodiment comprises a Li ion recovery tank equipped with a Li permselective membrane that recovers only Li ions from a lithium ion extract extracted from a treatment component of a lithium secondary battery, a recovery liquid storage tank that stores the recovery liquid from which the Li ions have been recovered, a temperature adjustment means that adjusts the temperature of the recovery liquid to 50° C. or higher, and a separation device that separates lithium hydroxide from the recovery liquid. Furthermore, the lithium hydroxide manufacturing apparatus of this embodiment preferably comprises a crystallization device, and preferably comprises filtrate recovery means that adds filtrate produced in the crystallization device to the recovery liquid. The method for producing lithium hydroxide according to the present embodiment can be easily carried out by the apparatus for producing lithium hydroxide according to the present embodiment.

[0054] 1 and 2 are flow diagrams showing a typical preferred embodiment of an apparatus for producing lithium hydroxide according to the present embodiment, which can be used to perform the method for producing lithium hydroxide according to the present embodiment. The flow diagram in Fig. 1 shows a case in which a crystallizer is used as a separation apparatus for separating lithium hydroxide from a recovered solution and cooling crystallization is used as the crystallization method, while Fig. 2 is a flow diagram in which evaporative crystallization is used. The methods for producing lithium hydroxide shown in Figs. 1 and 2 also include a filtrate recovery means for adding a filtrate produced in the crystallizer to the recovered solution.

[0055] 1 includes a Li-ion recovery tank 10, a recovery liquid storage tank 11 for storing a recovery liquid, a crystallizer 12 for crystallizing the recovery liquid (Li-ion-containing recovery liquid B2) obtained by recovering Li ions in the Li-ion recovery tank 10, heat exchangers 13a, 13b, and 13c, and a dryer 14. The Li-ion recovery tank 10 includes a raw liquid tank 10a for storing raw liquid A, a recovery liquid tank 10b for storing recovery liquid B1, and a Li-permselective membrane 10c. The Li-permselective membrane 10c includes a first electrode 10d (anode) on one main surface (the raw liquid A side) and a second electrode 10e (cathode) on the other main surface (the recovery liquid B side). The recovery liquid storage tank 11 includes a temperature adjustment means 11a for adjusting the temperature of the recovery liquid to 50°C or higher.

[0056] 2, like the production apparatus shown in Fig. 1, includes a Li-ion recovery tank 10, a storage tank 11 for storing a recovery liquid, a crystallizer 12 that crystallizes the recovery liquid and is a separation device that separates lithium hydroxide from a Li-ion-containing recovery liquid B2, heat exchangers 13a, 13b, and 13c, and a dryer 14. The Li-ion recovery tank 10 includes a raw liquid tank 10a for storing raw liquid A, a recovery liquid tank 10b for storing recovery liquid B, and a Li-permselective membrane 10c. The Li-permselective membrane 10c includes a first electrode 10d (anode) on one main surface side (raw liquid A side) and a second electrode 10e (cathode) on the other main surface side (recovered liquid B side). The recovery liquid storage tank 11 includes a temperature adjustment means 11a that can adjust the temperature of the recovery liquid to 50°C or higher. However, the apparatus differs in that a recovery line for filtrate C discharged from the crystallizer 12, which serves as a separation device, is provided. In the Li ion recovery tank 10 of Figures 1 and 2, oxygen and hydrogen may be generated in the raw liquid tank 10a and the recovered liquid tank 10b by electrolysis of water, so it is preferable to provide piping or the like that can evacuate or recover these.

[0057] In the Li ion recovery tank 10, the Li ions contained in the raw solution A are transferred from the raw solution A to the recovery liquid B1 using the Li permselective membrane 10c and recovered in the recovery liquid B1, and the recovery liquid B1 is supplied to the crystallizer 12 via the recovery liquid storage tank 11 as the Li ion-containing recovery liquid B2. 1 and 2, a heat exchanger 13a is provided to heat the Li-ion-containing recovery solution B2 to a predetermined temperature. The heat exchanger 13a may be a shell-tube type heat exchanger using a medium as shown in FIG. 1, or a jacket type or heater type heat exchanger using electricity or a heat medium. The heat source may be waste heat from cooling crystallization or excess heat generated by evaporation crystallization. The same applies to the heat exchangers 13b and 13c described below.

[0058] In the production apparatus of FIG. 1, lithium hydroxide crystallized in crystallizer 12, which is a separation device, and the filtrate produced by the crystallization are separated by solid-liquid separation or the like, and the lithium hydroxide is further dried in dryer 14, and lithium hydroxide monohydrate (LiOH HO) is extracted as a product.

[0059] The filtrate C, together with newly supplied pure water as needed, is heated in heat exchanger 13b as needed, and then passes through the recovered liquid storage tank 11 as recovered liquid B0 that is substantially free of Li ions, and is heated in heat exchanger 13c as needed, before being supplied to the recovered liquid tank 10b of the Li ion recovery tank 10. Note that the phrase "recovered liquid B0 substantially free of Li ions" means that the recovered liquid B0 does not contain any Li ions, since if it does not contain filtrate C, water such as pure water would become recovered liquid B0, and that if it does contain filtrate C, the filtrate C may contain Li ions, but since it is obtained by crystallizing lithium hydroxide from recovered liquid B1 stored in the recovered liquid tank 10b and Li ion-containing recovered liquid B2 supplied to the crystallizer 12 and thereby removing Li ions, the Li ion content is lower than that of these recovered liquids B1 and B2.

[0060] As described above, the production apparatus of this embodiment preferably includes a filtrate recovery means 15 that adds the filtrate produced in the crystallizer to the recovered liquid. The production apparatus shown in FIGS. 1 and 2 also includes a filtrate recovery means 15, specifically a line from the crystallizer 12 (a separation apparatus) to the recovered liquid storage tank 11, through which the filtrate C produced by crystallization in the crystallizer 12 is added to the recovered liquid. As shown in FIGS. 1 and 2, the filtrate recovery means 15 may include a heat exchanger 13b that serves as a temperature control means and a line for supplying pure water to the recovered liquid. Furthermore, although not shown in FIGS. 1 and 2, the filtrate recovery means 15 may also include a pump for pressure-feeding the filtrate and a meter such as a flow meter, if necessary.

[0061] 2 employs evaporative crystallization, vapor is discharged from crystallizer 12 by reducing pressure or the like, and cooled distilled water is recovered as filtrate C. Similarly to the production apparatus of FIG. 1, crystallized lithium hydroxide and liquid filtrate are produced, and the liquid filtrate is also recovered as filtrate C. In this way, filtrate recovery means 15 may be provided with a line for supplying the cooled distilled water to the recovered liquid, in addition to the line for supplying pure water to the recovered liquid as shown in FIG.

[0062] The Li-ion recovery tank 10 may be in the form of a single tank separated into a raw liquid tank 10a and a recovery liquid tank 10b by a Li-selective permeable membrane 10c, or may be in the form of two tanks, the raw liquid tank 10a and the recovery liquid tank 10b, connected via the Li-selective permeable membrane 10c.

[0063] In the manufacturing apparatus of FIG. 1 , the temperature adjusted to 50°C is the temperature of the recovery liquid in the recovery liquid tank 10b. To adjust the recovery liquid B1 in the recovery liquid tank 10b to 50°C, at least one of the heat exchangers 13b and 13c may be used before supplying the recovery liquid B0 to the recovery liquid tank 10b, or a temperature adjustment means 11a provided in the recovery liquid storage tank 11 may be used. For example, if the manufacturing apparatus does not have the temperature adjustment means 11a, the temperature of the recovery liquid B0 at the outlet of at least one of the heat exchangers 13b and 13c may be heated to a temperature higher than 50°C, thereby adjusting the temperature of the recovery liquid in the recovery liquid tank 10b to 50°C. Furthermore, if the temperature adjustment means 11a is provided and used, the temperature of the recovery liquid B0 at the outlet of the heat exchanger 13b does not need to be heated to 50°C. A temperature adjustment means equivalent to the temperature adjustment means 11a in the recovery liquid storage tank 11 may be provided in the recovery liquid tank 10b.

[0064] From the viewpoint of more reliably and stably adjusting the recovered liquid to 50° C., it is preferable to provide a temperature adjusting means 11a together with a heat exchanger 13b as shown in FIG. Furthermore, in addition to heating the recovery liquid B0, the heat exchanger 13c is useful for adjusting the temperature of the recovery liquid in the recovery liquid tank 10b to 50°C when performing a batch operation in which the recovery liquid is circulated between the recovery liquid tank 10b and the recovery liquid storage tank 11 until the concentration of Li ions contained in the recovery liquid B1 increases to a certain concentration.

[0065] As described above, it is also possible to adjust the temperature of the raw liquid, and a corresponding temperature heating means (not shown) may be provided. In this case, as with the recovered liquid, a raw liquid storage tank and a heat exchanger may be provided, and the raw liquid may be heated by the heat exchanger while circulating between the raw liquid tank 10a and the storage tank. Alternatively, a heat exchanger may be provided in the raw liquid storage tank for heating, or a heat exchanger may be provided in the raw liquid tank 10a. The filtrate line from the crystallizer 12 to the recovered liquid storage tank 11 and the lines supplying the recovered liquid, such as the lines supplying pure water and distilled water, may be provided with insulation for heat retention, and may also be provided with a jacket-type or heater-type heat exchanger using electricity, a heat medium, or the like for heat retention or heating.

[0066] The production apparatus preferably includes a recovered liquid storage tank 11 . The provision of the recovery liquid storage tank 11 facilitates batch-type operation in which the recovery liquid is circulated between the recovery liquid storage tank 10b and the recovery liquid storage tank 11 until the Li ion concentration contained in the recovery liquid B1 increases to a certain level, and also enables a variety of operations, such as circulating and heating the recovery liquid when starting up the manufacturing equipment, or storing the filtrate before supplying it to the recovery liquid tank as the recovery liquid. Furthermore, the combination of the heat exchanger 13c and the temperature adjustment means 11a facilitates the batch-type operation and heating of the recovery liquid when circulating it when starting up the manufacturing equipment, making it possible to more reliably and stably adjust the temperature of the recovery liquid to 50°C.

[0067] The temperature adjustment means 11a is not particularly limited as long as it is a means capable of adjusting the temperature of the recovered liquid, and may be, for example, a heat exchanger or may take the form of an air conditioning device that heats the entire recovered liquid storage tank 11. When a heat exchanger is employed, there are no particular limitations on its type and it may be selected appropriately depending on the mode of use. As with the heat exchangers 13a to 13c described above, for example, a shell-tube heat exchanger using a medium, a jacket type using electricity or a heat medium, or a heater type heat exchanger can be employed. When heating, the heat source can be waste heat from cooling crystallization, excess heat generated by evaporation crystallization, or the like.

[0068] The crystallizer 12 is a device provided for crystallizing lithium hydroxide from the recovery liquid (Li-ion-containing recovery liquid) obtained by recovering Li ions in the Li-ion recovery tank 10. In the case of a batchwise operation in which the recovery liquid is circulated between the recovery liquid tank 10b and the recovery liquid storage tank 11 until the concentration of Li ions contained in the recovery liquid B1 increases to a certain concentration, for example, the crystallization can be performed by extracting a part or all of the recovery liquid B1 as a Li-ion-containing recovery liquid B2 after the concentration has increased to the certain concentration and sending it to the crystallizer 12.

[0069] As described above, the crystallizer 12 employs cooling crystallization, evaporation crystallization, or the like for crystallization, and therefore, an appropriate device may be employed depending on the type of crystallization, and a commercially available crystallizer may also be used. In order to accelerate the precipitation of solids during crystallization, seed crystals of a lithium hydroxide compound may be added, and the crystallizer 12 may be equipped with a device for adding seed crystals. Furthermore, the crystallizer 12 may be equipped with a device for separating the crystallized lithium hydroxide from the filtrate, such as a solid-liquid separator, as necessary.

[0070] When cooling crystallization is employed as the crystallization method, as in the production apparatus of FIG. 1, an inert gas supply line, a pressure control valve for exhausting gas according to the pressure inside the crystallizer 12, and an exhaust line may be provided to maintain a positive pressure by supplying and exhausting an inert gas. Furthermore, when evaporative crystallization is employed as the crystallization method, as in the production apparatus shown in FIG. 2, the apparatus may be equipped with a pressure reducing device for discharging the filtrate generated in the apparatus as water vapor, and may also be equipped with a cooling device for cooling the filtrate discharged as water vapor to form a liquid filtrate, i.e., distilled water.

[0071] The drying device 14 is a device that dries the lithium hydroxide that contains water and that was not completely separated after the lithium hydroxide crystallized in the crystallizer 12 is separated from the filtrate by solid-liquid separation or the like, to produce lithium hydroxide monohydrate (LiOH HO) or anhydrous lithium hydroxide. The dryer used in the drying device 14 may be appropriately selected depending on the desired degree of drying, scale, etc., and may be, for example, a heater such as a hot plate, a horizontal dryer having a heating means and a feeding mechanism, a horizontal vibration fluidized dryer, or a commercially available Henschel mixer or FM mixer that can heat and dry at about 50 to 140°C under a reduced pressure atmosphere of usually about 1 to 80 kPa while stirring.

[0072] [Method for producing lithium sulfide] The method for producing lithium hydroxide of this embodiment can be applied to the following method for producing lithium sulfide, i.e., a method for producing lithium sulfide that includes supplying hydrogen sulfide to a recovery solution in the method for producing lithium hydroxide of the embodiment described above, or supplying hydrogen sulfide to lithium hydroxide obtained by the method for producing lithium hydroxide described above.

[0073] There are no particular limitations on the method for supplying hydrogen sulfide. When hydrogen sulfide is supplied to a recovery liquid, it may be supplied by blowing hydrogen sulfide gas into the recovery liquid. Lithium sulfide and water are produced by a reaction between lithium hydroxide and hydrogen sulfide, and the produced water is removed appropriately. Finally, lithium sulfide is obtained by stopping the blowing of hydrogen sulfide when the water has been substantially removed. When hydrogen sulfide gas is supplied to the recovery liquid, the hydrogen sulfide gas may be supplied to a crystallizer in the lithium hydroxide manufacturing apparatus, that is, the hydrogen sulfide gas may be blown into the Li ion-containing recovery liquid to cause a reaction. Alternatively, the Li ion-containing recovery liquid may be supplied to a separate reaction vessel, and the hydrogen sulfide gas may be blown into the reaction vessel in either a closed system (batch system) or a flow system to cause a reaction.

[0074] Furthermore, when hydrogen sulfide is supplied to lithium hydroxide, lithium sulfide can be obtained, for example, by charging lithium hydroxide and hydrogen sulfide gas into a reaction vessel and reacting them while stirring, etc. In this case, lithium hydroxide may be in the form of a hydrate or anhydrous, and in consideration of efficiency, it is preferable to react the lithium hydroxide as a hydrate with hydrogen sulfide.

[0075] The reaction temperature between lithium hydroxide and hydrogen sulfide may usually be 120° C. or higher and 300° C. or lower, preferably 140° C. or higher and 230° C. or lower, more preferably 150° C. or higher and 220° C. or lower, and even more preferably 160° C. or higher and 210° C. or lower. When the reaction temperature is within the above range, the reaction is promoted, and high-purity lithium sulfide with a reduced amount of residual lithium hydroxide is more likely to be obtained. The reaction time is preferably 1 hour or more and 60 hours or less, more preferably 2 hours or more and 30 hours or less, and even more preferably 6 hours or more and 20 hours or less. In this specification, the reaction time means the time during which hydrogen sulfide is brought into contact with lithium hydroxide and reacted, more specifically, the time from when the supply of hydrogen sulfide starts to when the supply is stopped.

[0076] The lithium sulfide thus obtained can be purified as needed. The purification method is not particularly limited, and may be carried out according to a conventional method. [Example]

[0077] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0078] (Lithium hydroxide manufacturing equipment) The production apparatus used was the one shown in FIG. 2, which had, in this order, a Li ion recovery tank separated into a raw liquid tank and a recovery liquid tank by a Li permselective membrane, a recovery liquid storage tank, a crystallization device capable of cooling and crystallizing as a separation device, and a heat exchanger (heat exchanger 13b) as a temperature control means.

[0079] The crystallization apparatus used as the separation device was a device equipped with a separable flask equipped with a stirring blade and a thermometer in a thermostatic bath. The separable flask had a nitrogen supply means to adjust the supply and exhaust of nitrogen (an inert gas) so that crystallization could be carried out under positive pressure. The crystallization apparatus also had a solid-liquid separation device, which was a flask equipped with a filter section equipped with filter paper and a connection section at the top to an aspirator, housed in a glove bag (the inside of which could be purged with nitrogen as necessary).

[0080] (Preparation of Lithium Permselective Membrane) The Li permselective membrane used was prepared as follows. The constituent material is lithium lanthanum titanate (Li 0.29 La 0.57 A lithium permselective membrane body was fabricated using LLTO (LiO3), and one of the main surfaces of the body was exposed to hydrochloric acid at 60°C for 5 days, thereby obtaining a lithium permselective membrane in which a lithium adsorption layer (HLTO) was formed on one of the main surfaces of the lithium permselective membrane body (LLTO).

[0081] (Determination of yield and purity of lithium hydroxide) The solid (also referred to as "cake") obtained by filtration using the solid-liquid separation device of the lithium hydroxide manufacturing apparatus was transferred to a petri dish and dried at 40°C for 2 hours in a vacuum dryer (corresponding to a "drying device") to obtain a dried cake. The dried cake was weighed and used as the yield of lithium hydroxide monohydrate in each Example and Comparative Example, and the purity was measured by neutralization titration.

[0082] Example 1 As a simulated lithium ion extract extracted from the treated components of a lithium secondary battery, 2 L of 3.0 M lithium hydroxide aqueous solution (pH 14.6) (lithium hydroxide content: 126 g (as lithium hydroxide monohydrate)) was used. The extract was placed in the raw solution tank of the manufacturing equipment, and 200 mL of 3.0 M lithium hydroxide aqueous solution was placed in the recovery solution tank, to which nitrogen was supplied. Next, while the temperature of the recovery solution in the recovery solution tank was adjusted to 80°C with an electric heater, a voltage of 5 V was applied to both sides of the Li permselective membrane, and Li ions were recovered in the recovery solution. A portion (7.5 mL) of the recovered solution from which Li ions had been recovered after 20 hours of voltage application was placed in a separable flask of a crystallizer without exposing it to the air, and while supplying nitrogen to the separable flask, the temperature of the thermostatic bath was set to 25°C to maintain the recovered solution in the separable flask at 25°C, and cooling crystallization was performed at a crystallization temperature of 25°C. The lithium hydroxide concentration in the recovered solution was 6.0 M as lithium hydroxide monohydrate. The liquid in the separable flask containing lithium hydroxide precipitated by the cooling crystallization was then placed in a nitrogen-filled glove bag to prevent contact with the atmosphere, and the liquid was placed in a filter section equipped with filter paper in a solid-liquid separator housed in the glove bag. Filtration was carried out while reducing the pressure with an aspirator, yielding lithium hydroxide monohydrate. The yield of the obtained lithium hydroxide monohydrate, as measured by the above method, was 1.89 g, and its purity was 99.7%. In this Example 1, crystallization (crystallization in a separable flask and filtration in a solid-liquid separator) was carried out in the presence of an inert gas, and therefore this was considered to be the crystallization environment in which lithium hydroxide was produced under an "inert" atmosphere. In other Examples and Comparative Examples, "inert" also means that crystallization was carried out in the presence of an inert gas.

[0083] Example 2 In Example 1, a portion (7.5 mL) of the recovered liquid from which Li ions had been recovered after 20 hours of voltage application was cooled and crystallized in the same manner as in Example 1. The entire portion was then filtered using a solid-liquid separator, and the resulting filtrate and pure water were added to form a liquid (total: 7.5 mL) which was returned to the recovered liquid storage tank. While adjusting the temperature of the recovered liquid in the recovered liquid tank to 80°C using an electric heater, a voltage of 5 V was applied for 1.5 hours. A portion (7.5 mL) of the recovered liquid from which Li ions had been recovered was cooled and crystallized in the same manner as in Example 1, and filtered using a solid-liquid separator to obtain lithium hydroxide. The yield of the obtained lithium hydroxide was 1.92 g, and its purity was 99.6%.

[0084] Comparative Example 1 Lithium hydroxide was obtained in the same manner as in Example 1, except that the temperature of the recovered liquid was changed from 80°C to 45°C.

[0085] Comparative Example 2 Lithium hydroxide was obtained in the same manner as in Example 1, except that the temperature of the recovered liquid was changed from 80°C to 45°C and the crystallization operation was carried out in the atmosphere without supplying nitrogen to the separable flask in the crystallizer.

[0086] [Table 1]

[0087] The results of the above examples confirmed that the method for producing lithium hydroxide according to the present embodiment does not require a dehydration step such as heating and concentration, and therefore can produce lithium hydroxide with less energy. It also confirmed that high-purity lithium hydroxide can be produced in high yield. On the other hand, it was confirmed that the yield was extremely low in Comparative Examples 1 and 2, in which the recovery liquid temperature was 45° C. Furthermore, in Comparative Example 2, in which the crystallization environment was air, the purity was reduced, and it was also confirmed that an inert crystallization environment is preferable to obtain lithium hydroxide of higher purity. [Explanation of symbols]

[0088] 10. Lithium ion recovery tank 10a. Raw solution tank 10b. Recovery liquid tank 10c. Lithium permselective membrane 10d.First electrode 10e.Second electrode 11.Recovered liquid storage tank 11a: Temperature control means 12.Crystallizer 13a. Heat exchanger 13b.Heat exchanger 13c.Heat exchanger 14.Drying equipment 15. Filtrate collection means A: Undiluted solution B0: Recovered liquid B1: Recovery liquid (in recovery liquid tank) B2: Li-ion-containing recovery liquid C: Filtrate

Claims

1. A method for producing lithium hydroxide from a lithium ion extract solution extracted from a treatment component of a lithium secondary battery, by recovering only Li ions into a recovery solution using a Li permselective membrane, the method comprising: The temperature of the recovered liquid is adjusted to 50°C or higher while the recovered liquid is recovered; and separating lithium hydroxide from the recovered solution; Including, The separation is carried out by crystallization, The method for producing lithium hydroxide, wherein the crystallization is carried out using an inert gas or a gas having a carbon monoxide, carbon dioxide, and hydrocarbon concentration of 10 ppm or less in the recovered liquid to be subjected to the crystallization.

2. A method for producing lithium hydroxide from a lithium ion extract solution extracted from a treatment component of a lithium secondary battery, by recovering only Li ions into a recovery solution using a Li permselective membrane, the method comprising: The temperature of the recovered liquid is adjusted to 50°C or higher while the recovered liquid is recovered; and separating lithium hydroxide from the recovered solution; Including, The separation is carried out by crystallization, The method for producing lithium hydroxide, wherein the crystallization is carried out using an inert gas in a recovered liquid to be subjected to the crystallization.

3. 3. The method for producing lithium hydroxide according to claim 1, wherein the temperature is 80°C or higher and 100°C or lower.

4. The method for producing lithium hydroxide according to any one of claims 1 to 3, wherein the crystallization is cooling crystallization.

5. 5. The method for producing lithium hydroxide according to claim 4, wherein the cooling and crystallization is carried out while maintaining a positive pressure by blowing an inert gas into the recovered liquid to be subjected to the crystallization.

6. 6. The method for producing lithium hydroxide according to claim 4, wherein the cooling crystallization is carried out while adjusting the temperature of the recovered solution to be subjected to the crystallization to 40°C or less.

7. The method for producing lithium hydroxide according to any one of claims 1 to 3, wherein the crystallization is evaporative crystallization.

8. The method for producing lithium hydroxide according to claim 7, further comprising adding pure water produced by the evaporation and crystallization to the filtrate or the recovered liquid.

9. The method for producing lithium hydroxide according to any one of claims 1 to 8, further comprising adding a filtrate produced by the crystallization to the recovered solution.

10. The method for producing lithium hydroxide according to claim 9, wherein the filtrate is heated.

11. The method for producing lithium hydroxide according to claim 10, wherein the heating utilizes exhaust heat or excess heat from the crystallization.

12. The method for producing lithium hydroxide according to any one of claims 9 to 11, wherein impurities are not removed when the filtrate is added to the recovered liquid.

13. The method for producing lithium hydroxide according to any one of claims 1 to 12, wherein the Li permselective membrane contains an oxide or oxynitride containing Li.

14. a Li ion recovery tank equipped with a Li selective permeable membrane that recovers only Li ions from a lithium ion extract extracted from a treatment component of a lithium secondary battery; a recovery liquid storage tank for storing a recovery liquid for recovering the Li ions; a temperature adjusting means for adjusting the temperature of the recovery liquid to 50°C or higher; and a separation device for separating lithium hydroxide from the recovered solution; Equipped with The apparatus for producing lithium hydroxide, wherein the separation device is a crystallization device that supplies an inert gas or a gas having carbon monoxide, carbon dioxide, and hydrocarbon concentrations of 10 ppm or less to the recovered liquid to be subjected to the crystallization.

15. a Li ion recovery tank equipped with a Li selective permeable membrane that recovers only Li ions from a lithium ion extract extracted from a treatment component of a lithium secondary battery; a recovery liquid storage tank for storing a recovery liquid for recovering the Li ions; a temperature adjusting means for adjusting the temperature of the recovery liquid to 50°C or higher; and a separation device for separating lithium hydroxide from the recovered solution; Equipped with The apparatus for producing lithium hydroxide, wherein the separation device is a crystallization device that supplies an inert gas to the recovered liquid to be subjected to the crystallization.

16. 16. The apparatus for producing lithium hydroxide according to claim 14 or 15, further comprising a filtrate recovery means for adding the filtrate produced in the crystallizer to the recovered liquid.

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