JP7806991B2 - How to manufacture lithium hydroxide - Google Patents

Description

The present invention relates to a method for producing lithium hydroxide.

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

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

Sulfide solid electrolytes are known as solid electrolytes used in lithium secondary batteries and other devices. Because sulfide solid electrolytes have high ionic conductivity, they are useful for increasing the output of batteries. Lithium sulfide is commonly used as a raw material in the production of sulfide solid electrolytes, and there is growing demand for lithium hydroxide, which is the raw material for lithium sulfide. One method for producing lithium hydroxide involves electrolyzing an aqueous lithium carbonate solution or suspension and passing it through an ion exchange membrane to produce an aqueous lithium hydroxide solution (see, for example, Patent Document 2).

JP 2019-81953 A JP 2009-270188 A

The technology described in Patent Document 1 uses a lithium ion conductor to recover lithium ions from a source solution containing lithium ions. However, with the increasing demand for lithium, there is an ever-increasing need 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 raw materials, such as aqueous solutions containing lithium. Furthermore, obtaining lithium hydroxide using the technology described in Patent Document 2 requires a dehydration process, such as heating and concentration, which consumes a lot of energy. Therefore, reducing this energy consumption is necessary to obtain lithium more cheaply.

The present invention was made in light of these circumstances, and aims to provide a method and apparatus for producing high-purity lithium hydroxide efficiently using less energy.

As a result of extensive research into resolving the above-mentioned problems, the inventors have discovered that the following invention can solve these problems.

1. A method for producing lithium hydroxide from a lithium ion extract 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 method comprising:
recovering the recovered solution while adjusting the temperature of the recovered solution to 50°C or higher; 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 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 the above 4 or 5, 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 3 above, wherein the crystallization is evaporative crystallization.
8. The method for producing lithium hydroxide according to the above item 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 3 to 8 above, further comprising adding a filtrate produced by the crystallization to the recovered solution.
10. The method for producing lithium hydroxide according to 9 above, wherein the filtrate is heated.
11. The method for producing lithium hydroxide according to the above 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 items 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 selective permeable 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 recovered liquid to 50°C or higher; and a separation device for separating lithium hydroxide from the recovered liquid.
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 apparatus for producing lithium hydroxide according to the above item 15, further comprising a filtrate recovery means for adding the filtrate produced in the crystallizer to the recovery liquid.

The present invention provides a method and apparatus for producing high-purity lithium hydroxide efficiently and with less energy.

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. 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.

The following describes a lithium hydroxide production method and lithium hydroxide production apparatus according to one embodiment of the present invention (hereinafter referred to as "this embodiment"). Note that the lithium hydroxide production method and lithium hydroxide production apparatus according to one embodiment of the present invention are merely one embodiment of the lithium hydroxide production method and lithium hydroxide production apparatus of the present invention, and the present invention is not limited to the lithium hydroxide production method and lithium hydroxide production apparatus of one embodiment of the present invention. Furthermore, in this specification, "lithium" refers to both lithium and lithium ions, and should be interpreted appropriately unless a technical contradiction arises.

[Method of producing 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 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 of this embodiment, 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, and a wide range of source solutions can be used, 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 of this embodiment enables the production of high-purity lithium hydroxide efficiently and with less energy.

[Recovering only Li ions in the recovery solution]
In the method for producing lithium hydroxide according to the present embodiment, only Li ions are recovered into a recovered solution using a Li permselective membrane from a lithium ion extract (sometimes simply referred to as the "stock solution") extracted from a processing component of a lithium secondary battery, which serves as a stock solution containing an Li aqueous solution. Here, "Li ions only" means that the extract is substantially free of ions other than Li ions, and the content of the other ions is 0.5% by mass or less.

(undiluted solution)
The stock solution containing the Li ion aqueous solution can be any solution containing Li ions without any particular limitation, 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 extracts may be used alone or in combination.

In this embodiment, the sulfide-based solid electrolyte refers to a solid electrolyte containing at least lithium and sulfur elements, and typical examples include those containing lithium, sulfur, and phosphorus elements such as Li ₂ S-P ₂ S ₅ , and further containing halogen elements such as Li ₂ S-P ₂ S ₅ -LiI, Li ₂ S-P ₂ S ₅ -LiCl, Li ₂ S-P ₂ S ₅ -LiBr, Li ₂ S-P ₂ S ₅ -LiI-LiBr, Li ₂ S-P ₂ S ₅ -Li ₂ O-LiI, and Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI.

Regarding Li ion extracts extracted from processing components of lithium secondary batteries containing sulfide-based solid electrolytes, a typical example is an aqueous solution of sulfide-based solid electrolyte obtained by dissolving the sulfide-based solid electrolyte used in the lithium secondary battery in an alkaline aqueous solution.

Preferred examples of alkaline components in the alkaline aqueous solution for dissolving sulfide-based solid electrolytes 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 perspective of ease of dissolving sulfide-based solid electrolytes, sodium hydroxide, potassium hydroxide, and calcium hydroxide are more preferred as alkaline components.

The Li ion extract used as the raw solution can be prepared using a commonly known, general electrodialysis device. In the electrodialysis device, monovalent cations such as Li ions (Li ⁺ ) and Na ions (Na ⁺ ) permeate the cation exchange membrane and migrate to the cathode (treatment solution), while other polyvalent cations have low permeability to the cation exchange membrane, and negative ions do not permeate the cation exchange membrane. Therefore, the Li ions (Li ⁺ ) to be recovered migrate from the raw solution to the treatment solution. Furthermore, OH ⁻ ions are generated at the cathode by electrolysis of water. Therefore, using the electrodialysis device, Li ions in the raw solution can be transferred to the treatment solution, while the treatment solution can be made alkaline. However, in this electrodialysis treatment, other monovalent cations such as Na ions (Na ⁺ ) (non-Li monovalent cations) also migrate to the treatment solution along with Li ions. Therefore, by using the treatment solution after electrodialysis as the raw solution, Li ions can be selectively recovered in the recovery solution.

In other words, if the Li ion extract is non-alkaline, an alkaline aqueous solution (treatment 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 with high efficiency in the recovery solution.

(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.

(Adjusting the temperature of the recovered liquid)
In this embodiment, when recovering 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 adjusting the temperature of the recovery solution to 50°C or higher, Li ions can be recovered with high efficiency. In other words, adjusting the temperature to 50°C or higher increases the solubility of lithium ions in the recovery solution, and lithium ions are supplied from the raw solution in proportion to the increased solubility, allowing a large amount of lithium ions to be recovered. Furthermore, by crystallizing the heated recovery solution, it becomes possible to produce lithium hydroxide while reducing energy consumption.

In this embodiment, the temperature of the recovery liquid adjusted when recovering Li ions is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher, with an upper limit of 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. Since the actual temperature of the recovery liquid may fluctuate above or below this set value, the actual temperature of the recovery liquid is considered to include a range of less than ±2.0°C. The same applies to the temperature of the raw liquid, which will be described later.

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

In this embodiment, there are no particular limitations on the means for controlling the pH of the stock solution, but it may be performed, for example, by adding an alkaline aqueous solution to the stock solution. Furthermore, the pH of the stock solution may be controlled when recovering Li ions into the recovery solution; that is, Li ions may be recovered into the recovery solution while controlling the pH of the stock solution, or it may be controlled in advance before recovering Li ions into the recovery solution.

Preferred examples of alkaline components in 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. Of these, sodium hydroxide is more preferred from the viewpoint of being able to quickly adjust the pH of the lithium ion extract.

The temperature of the raw solution may be adjusted in the same way as the recovery solution, specifically, it may be heated. 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 adjusted temperature should be within the temperature adjustment range of the recovery solution described above.

(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) having particularly high ionic conductivity, and a Li-adsorption layer formed as a thin layer on the source liquid side thereof.
When a super Li ion conductor is used as the Li permselective membrane body, the ionic current of Li ions flowing between the electrodes is increased, thereby improving the Li recovery efficiency. Here, the Li ions contained in the aqueous solution exist as Li hydrated ions with water molecules coordinated around them. Therefore, in order to further increase the ionic current, it is effective to create a situation 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 formed by modifying the surface of the material that constitutes the Li permselective membrane is preferably mentioned.

Preferred examples of materials constituting the Li permselective membrane body include 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: Li ₇ La ₃ Zr ₂ O ₁₂ (hereinafter also referred to as "LLZO"), lithium lanthanum niobate: Li ₅ La ₃ Nb ₂ O ₁₂ , and lithium lanthanum tantalate: Li ₅ La ₃ Ta ₂ O _12. More specifically, Li _0.29 La _0.57 TiO ₃ (a≈0.1, b≈0) can be used as LLTO.

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

Examples of super Li ion conductors that can be used as a material for constituting the Li permselective membrane body include, in addition to the above-mentioned LLTO, LLZO, and the like, Li-containing oxides, such as Li _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) (Li ₂ O—Al ₂ O ₃ —SiO ₂ —P ₂ O ₅ —TiO ₂ —GeO ₂ system, hereinafter also referred to as “LASiPTiGeO”), which is a Li-substituted NASICON (Na Super Ionic Conductor) type crystal.

Preferred examples of oxynitrides containing Li include lithium phosphate oxynitride (Li ₃ PON, hereinafter also referred to as "LiPON"), nitride of LLTO (LLTON), nitride of LLZO (LLZON), nitride of LASiPTiGeO (LASiPTiGeON), and the like.

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

Here, if a large amount of Li ions in particular are adsorbed onto the surface of the Li permselective membrane body using 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).

The Li permselective membrane preferably has an anode and a cathode bonded thereto, with the anode being bonded to the source liquid side (one of the main surfaces) of the Li permselective membrane and the cathode being bonded to the recovered liquid side (the other main surface). With this configuration, the source liquid side main surface and the recovered liquid side main surface of the Li permselective membrane are maintained at a constant positive potential and a constant negative potential, respectively.
The anode and cathode may be made of any suitable metal material that does not undergo electrochemical reaction in the raw solution or recovered solution, such as SUS, Ti, or a Ti—Ir alloy.

The above materials used as Li-selective permeable membranes are solids, but 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-selective permeable membrane will flow by ionic conduction from the anode side (source solution) to the cathode side (recovered solution) of the Li-selective permeable membrane. The Li ions that reach the cathode side of the Li-selective permeable membrane are recovered in the recovered solution. Therefore, after a certain period of time has passed, the Li-ion concentration in the source solution decreases, and the Li-ion concentration in the recovered solution increases.

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-treating one main surface of the Li permselective membrane body (e.g., LLTO), for example by exposing this surface to hydrochloric acid or nitric acid for 5 days. This treatment is presumed to form a substance layer (HLTO) with a composition similar to H _0.29 La _0.57 TiO ₃ , in which Li, which is particularly susceptible to oxidation among the constituent elements of the Li permselective membrane body (e.g., LLTO), is replaced with hydrogen in the acid. Here, the formation of the thin surface layer (HLTO) is supported by the presence of peaks different from those of the Li permselective membrane body (e.g., LLTO) in the X-ray diffraction results in WO 2017/131051.

The H site in HLTO was originally intended to accommodate 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 reaction with acid, it is only formed on the outermost surface of the Li permselective membrane itself.

[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.

(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, the specific method is not particularly limited as long as it is carried out by a conventional cooling crystallization technique, and for example, it is preferable to carry out the crystallization while maintaining a positive pressure by blowing an inert gas into the Li ion-containing recovery liquid. Blowing in an inert gas can suppress the production of lithium carbonate (hereinafter sometimes simply referred to as "carbonation") and further promote the production of lithium hydroxide by cooling crystallization, allowing for more efficient production of high-purity lithium hydroxide.

When the recovery liquid is heated prior to crystallization, the heating temperature is preferably 50°C or higher, more preferably 60°C or higher, with an upper limit of 80°C or lower. When the heating temperature is within the above range, cooling crystallization can be carried out more efficiently.

There are no particular limitations on the positive pressure, and it is usually sufficient to set it to 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, or the like 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. In order to obtain lithium hydroxide of higher purity, a concentration of 1 ppm or less is preferred, and 0.1 ppm is more preferred.

In the case of cooling crystallization, it is preferable to adjust the temperature to 40°C or below in order to perform cooling crystallization more efficiently. For the same reason, the crystallization temperature is preferably 35°C or below, more preferably 30°C or below, and even more preferably 25°C or below. There is no particular lower limit, but it should be above 0°C, and preferably 3°C or above.

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.

(evaporation crystallization)
In evaporative crystallization, the recovered liquid is heated in the stage prior to crystallization, so that 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 normal 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 carrying out evaporative crystallization more efficiently, the adjusted temperature is more preferably 85°C or higher, and even more preferably 90°C or higher.

From the perspective of conducting evaporation crystallization more efficiently, it is preferable to carry out evaporation crystallization under a reduced pressure atmosphere. By reducing the pressure, water vapor generated within the system can be discharged and added to the filtrate or recovered liquid for recovery.

When reducing the pressure, there are no particular limitations on the pressure, and the vacuum pressure may usually be about 0.05 to 10 kPa, and from the viewpoint of more efficient evaporation and crystallization, the pressure 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, and in this case, nitrogen gas, argon gas, or the like may be used as the inert gas. 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. In order to obtain lithium hydroxide with higher purity, the concentration is preferably 1 ppm or less, and more preferably 0.1 ppm.

[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 discharged filtrate itself, which is a major advantage. Furthermore, the amount of new pure water used to supply 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.

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.
A filtrate is also produced in the case of cooling crystallization. Because this filtrate is produced by crystallizing lithium hydroxide from a Li-ion-containing recovery solution, it can be said to be a recovery solution from which Li ions have been removed and which is substantially free of Li ions. However, Li ions contained in the recovery solution may still be present. In this case, the filtrate may not be pure water, but it can be reused by adding it to the recovery solution, thereby reducing the amount of new pure water used and enabling more efficient production of lithium hydroxide. Thus, whether cooling crystallization or evaporative 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 liquid 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.

When adding the filtrate to the recovery liquid, the filtrate may be heated as needed. 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 raised, promoting the migration of Li ions from the raw solution to the recovery liquid and making it easier to recover Li ions in the recovery liquid, thereby enabling more efficient production of lithium hydroxide. When heating the filtrate, a temperature that raises the temperature of the recovery liquid to 50°C or higher is preferable, and more preferable temperatures are those that result in the more preferable adjustment temperatures 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.

In addition, when the filtrate is added to the recovery liquid, as mentioned above, the filtrate may contain Li ions. However, impurities other than Li ions are removed by the selectively permeable membrane, so the filtrate can be reused without the need for separate impurity removal.

The lithium hydroxide obtained by crystallization is usually a monohydrate (LiOH.H ₂ O). 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.

[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 Li ions have been recovered, temperature adjustment means that adjusts 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.

Figures 1 and 2 are flow diagrams showing a typical preferred embodiment of the lithium hydroxide production apparatus of this embodiment, which can be used to perform the lithium hydroxide production method of this embodiment. Figure 1 is a flow diagram showing a case in which a crystallizer is used as a separation device to separate lithium hydroxide from the recovery liquid, and cooling crystallization is used as the crystallization method, while Figure 2 is a flow diagram showing a case in which evaporative crystallization is used. Furthermore, the lithium hydroxide production methods shown in Figures 1 and 2 include a filtrate recovery means for adding the filtrate produced in the crystallizer to the recovery liquid.

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, which is a separation device for separating lithium hydroxide from 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 stock liquid tank 10a for storing stock 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 side (stock liquid A side) and a second electrode 10e (cathode) on the other main surface side (recovered liquid B side), and the recovery liquid storage tank 11 includes temperature adjustment means 11a for adjusting the temperature of the recovery liquid to 50°C or higher.

2, like the production apparatus shown in Fig. 1, has 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 apparatus 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 is equipped with a stock liquid tank 10a for storing stock liquid A, a recovery liquid tank 10b for storing recovery liquid B, and a Li permselective membrane 10c. The Li permselective membrane 10c is equipped with a first electrode 10d (anode) on one main surface side (stock liquid A side) and a second electrode 10e (cathode) on the other main surface side (recovered liquid B side), and the recovery liquid storage tank 11 is equipped with temperature adjustment means 11a that can adjust the recovery liquid to 50°C or higher, but differs in that a recovery line for filtrate C discharged from the crystallizer 12, which serves as a separation apparatus, 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, respectively, due to electrolysis of water, so it is preferable to provide piping or the like that can vent or recover these.

In the Li ion recovery tank 10, the Li ions contained in the raw solution A are transferred from the raw solution A to a recovery solution _B1 using a Li permselective membrane _10c and recovered in the recovery solution B1. The recovery solution _B1 is then supplied to a crystallizer 12 via a recovery solution storage tank 11 as a Li ion-containing recovery solution _B2 .
1 and 2, a heat exchanger 13a is provided that heats 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.

In the production apparatus of FIG. 1 , lithium hydroxide crystallized in a crystallizer 12, which is a separation device, and a filtrate produced by the crystallization are separated by solid-liquid separation or the like, and the lithium hydroxide is further dried in a dryer 14, and lithium hydroxide monohydrate (LiOH.H ₂ O) is extracted as a product.

The filtrate C is heated as needed in the heat exchanger 13b together with newly supplied pure water as needed, and then passes through the recovered liquid storage tank 11 as a recovered liquid _B0 that is substantially free of Li ions, and is heated as needed in the heat exchanger 13c, and then supplied to the recovered liquid tank 10b of the Li ion recovery tank 10. Note that the recovered liquid _B0 being substantially free of Li ions means that the recovered liquid B0 does not contain any Li ions at all, because if it does not contain filtrate C, water such as pure water would become the recovered liquid _B0 , and also means that if it contains filtrate C, although there is a possibility that the filtrate C may contain Li ions, the filtrate C is obtained by crystallizing lithium hydroxide from the recovered liquid _B1 stored in the recovered liquid tank 10b and the Li ion-containing recovered liquid B2 supplied to the crystallizer ₁₂ and thus the Li ion content is lower than in these recovered liquids _B1 and _B2 .

As previously mentioned, the manufacturing apparatus of this embodiment preferably includes a filtrate recovery means 15 that adds the filtrate produced in the crystallizer to the recovered liquid. The manufacturing apparatus shown in Figures 1 and 2 also includes a filtrate recovery means 15, and specifically, this corresponds to the line from the crystallizer 12 (a separation device) to the recovered liquid storage tank 11, where filtrate C produced by crystallization in the crystallizer 12 is added to the recovered liquid. As shown in Figures 1 and 2, the filtrate recovery means 15 may include a heat exchanger 13b, which corresponds to temperature control means, and a line for supplying pure water to the recovered liquid. Furthermore, although not shown in Figures 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.

Furthermore, the manufacturing apparatus of Figure 2 employs evaporative crystallization, so steam is discharged from the crystallizer 12 by reducing pressure or the like, and cooled distilled water is recovered as filtrate C. As with the manufacturing apparatus of Figure 1, crystallized lithium hydroxide and liquid filtrate are produced, and the liquid filtrate is also recovered as filtrate C. Thus, the filtrate recovery means 15 may be equipped 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 Figure 1.

The Li ion recovery tank 10 may be a single tank separated into a raw liquid tank 10a and a recovered liquid tank 10b by a Li selective permeable membrane 10c, or the two tanks, raw liquid tank 10a and recovered liquid tank 10b, may be connected via a Li selective permeable membrane 10c.

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.

From the viewpoint of more reliably and stably adjusting the temperature of the recovered liquid to 50° C., it is preferable to provide a temperature adjusting means 11 a together with a heat exchanger 13 b 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 a batch operation is performed 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.

As described above, it is also possible to adjust the temperature of the stock solution, and a corresponding temperature heating means may be provided (not shown). In this case, as with the recovered solution, a stock solution storage tank and a heat exchanger may be provided, and the stock solution may be heated by the heat exchanger while circulating between the stock solution tank 10a and the storage tank. Alternatively, a heat exchanger may be provided in the stock solution storage tank for heating, or a heat exchanger may be provided in the stock solution tank 10a.
Furthermore, the filtrate line from the crystallizer 12 to the recovered liquid storage tank 11 and the lines for supplying the recovered liquid, such as the lines for 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.

The production apparatus preferably includes a recovery 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 tank 10b and the recovery liquid storage tank 11 until the concentration of Li ions contained in the recovery liquid _B1 as described above increases to a certain concentration, and also enables a variety of operations, such as circulating and heating the recovery liquid at the start-up of the manufacturing apparatus, and 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 during circulation at the start-up of the manufacturing apparatus, making it possible to more reliably and stably adjust the recovery liquid to 50°C.

The temperature adjustment means 11a is not particularly limited as long as it is capable of adjusting the temperature of the recovered liquid. For example, it may be a heat exchanger, or it may take the form of an air conditioning unit that heats the entire recovered liquid storage tank 11. When a heat exchanger is used, there are no particular restrictions on its type and it can be selected appropriately depending on the usage mode. As with the heat exchangers 13a-c 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 used. When heating, the heat source can be the exhaust heat from cooling crystallization, excess heat generated by evaporation crystallization, etc.

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, after the concentration has increased to the certain concentration, part or all of the recovery liquid _B1 may be extracted as the Li-ion-containing recovery liquid _B2 and sent to the crystallizer 12 to perform the crystallization.

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.

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 in accordance with the pressure inside the crystallizer 12, and an exhaust line may be provided to maintain a positive pressure by supplying and exhausting the inert gas.
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.

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 has been separated from the filtrate by solid-liquid separation or the like, to produce lithium hydroxide monohydrate (LiOH.H ₂ O) or anhydrous lithium hydroxide.
The dryer used in the drying device 14 may be appropriately selected depending on the desired degree of drying, scale, and the like. 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 can also be used.

[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.

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.

When supplying hydrogen sulfide 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, the lithium hydroxide may be in the form of a hydrate or anhydrous, but from the perspective of efficiency, it is preferable to react the hydrate with hydrogen sulfide as is.

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 is started to when the supply is stopped.

The lithium sulfide obtained in this manner can be purified as needed. There are no particular restrictions on the purification method, and it can be carried out according to conventional methods.

The present invention will now be described in detail using examples, but the present invention is not limited to these examples in any way.

(Lithium hydroxide manufacturing equipment)
An apparatus was used which had, in the order shown in FIG. 2 , 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 13 b) as a temperature control means.

The crystallization device used as the separation device consisted of a thermostatically controlled bath and a separable flask equipped with a stirring blade and a thermometer. The separable flask had a nitrogen supply means that allowed for adjustment of the supply and exhaust of nitrogen (an inert gas) to enable crystallization under positive pressure. The crystallization device also had a solid-liquid separation device, consisting of a flask equipped with a filter paper filter and an aspirator connection at the top, housed in a glove bag (the inside of which could be replaced with nitrogen if necessary).

(Preparation of Li permselective membrane)
The Li permselective membrane used was prepared as follows.
A lithium permselective membrane body was prepared using lithium lanthanum titanate ( _{Li0.29La0.57TiO3} ) as _its constituent material, and one main surface of the body was exposed to hydrochloric acid at 60°C for 5 days to obtain a lithium permselective membrane in _which a lithium adsorption layer (HLTO) was formed on one main surface of the lithium permselective membrane body (LLTO).

(Determination of Lithium Hydroxide Yield and Purity)
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 apparatus") 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 also measured by neutralization titration.

Example 1
As a simulated lithium ion extract extracted from the treated components of a lithium secondary battery, 2 L of a 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 apparatus, and 200 mL of a 3.0 M lithium hydroxide aqueous solution was placed in a 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 containing lithium hydroxide precipitated by the cooling crystallization in the separable flask 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, and filtered while reducing the pressure with an aspirator to obtain 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 used as the crystallization environment, and lithium hydroxide was produced in an "inert" atmosphere. In other Examples and Comparative Examples, "inert" also means that crystallization was carried out in the presence of an inert gas.

Example 2
In Example 1, a portion (7.5 mL) of the recovered solution 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 solution storage tank. A voltage of 5 V was applied for 1.5 hours while the temperature of the recovered solution in the recovered solution tank was adjusted to 80°C using an electric heater. A portion (7.5 mL) of the recovered solution 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%.

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.

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 that the crystallization operation was carried out in the atmosphere without supplying nitrogen to the separable flask in the crystallizer.

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 was 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 recovered 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 in order to obtain lithium hydroxide of higher purity.

10. Li ion recovery tank 10a. Stock solution tank 10b. Recovery solution tank 10c. Li permselective membrane 10d. First electrode 10e. Second electrode 11. Recovery solution storage tank 11a: Temperature control means 12. Crystallizer 13a. Heat exchanger 13b. Heat exchanger 13c. Heat exchanger 14. Drying device 15. Filtrate recovery means A: Stock solution _B0 : Recovery solution _B1 : Recovery solution (in recovery solution tank)
_B2 : Li ion-containing recovery liquid C: Filtrate

Claims (16)

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:
recovering the recovered solution while adjusting the temperature of the recovered solution to 50°C or higher; 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 . 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:
recovering the recovered solution while adjusting the temperature of the recovered solution to 50°C or higher; 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. The method for producing lithium hydroxide according to claim 1 , wherein the temperature is 80°C or higher and 100°C or lower. The method for producing lithium hydroxide according to any one of claims 1 to 3 , wherein the crystallization is cooling crystallization. 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. 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. The method for producing lithium hydroxide according to any one of claims 1 to 3 , wherein the crystallization is evaporative crystallization. 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. 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. The method for producing lithium hydroxide according to claim 9 , wherein the filtrate is heated. The method for producing lithium hydroxide according to claim 10 , wherein the heating utilizes exhaust heat or excess heat from the crystallization. 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. 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. 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 recovered liquid to 50°C or higher; and a separation device for separating lithium hydroxide from the recovered liquid.
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 . 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 recovered liquid to 50°C or higher; and a separation device for separating lithium hydroxide from the recovered liquid.
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. 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.