Production of hydrogen and solid lithium hydroxide

Abstract

The problem addressed by the present invention is to identify a highly energy-efficient lithium hydroxide production process. This process should operate without using thermal energy. As a raw material, the process should be capable of processing the Li-containing water produced when used lithium-ion batteries are digested. The LiOH produced by this process should be of sufficiently high purity that it can be directly used in the production of new LIBs. The process should achieve high throughput and have low space requirements so that it can be combined with existing processes for the reprocessing of used LIBs or the production of new LIBs to form a closed, continuous production cycle. The process according to the present invention is an electrolytic membrane process operated using a LiSICon membrane. A particular aspect of this process is that the electrolysis is operated up to the precipitation limit of lithium hydroxide.

Description

[Technical Field]

[0001] Lithium (Li) is obviously required for the production of lithium-ion batteries (LIBs). Due to its high reactivity, lithium always exists naturally in a bound form, rather than as a pure substance. The starting material used in the production of LIBs is generally lithium in the form of lithium hydroxide (LiOH) or lithium carbonate (Li2CO3).

[0002] In most natural deposits, Li exists in the form of lithium oxide (LiO) or salts such as lithium sulfate (LiSO) or lithium chloride (LiCl). Lithium oxide is a component of ores such as pegmatites, while lithium sulfate and chloride exist in dissolved form in the leachate of Li salt lakes. During the mining process, the extracted lithium compound is converted to lithium carbonate (LiCO) in certain cases. In a further process step, lithium carbonate can be converted to lithium hydroxide by reaction with quicklime or calcium hydroxide. [Background technology]

[0003] The extraction of Li and its conversion to LiOH is described below: Wietelmann, U. and Steinbild, M. (2014). Lithium and Lithium Compounds. In Ullmann's Encyclopedia of Industrial Chemistry, (ed.). DOI:10.1002 / 14356007.a15_393.pub2 Although abundant lithium deposits are known, the production of LiOH from their lithium compounds is very energy intensive, generates large amounts of wastewater, and is a strategic necessity independent of the deposit owners.

[0004] One solution to this problem could be to reprocess materials from spent LIBs so that the lithium contained within them can be reused as a raw material for new batteries.

[0005] Recycling processes for LIBs have been developed to industrial maturity in the past, but most of them have focused on the metals Fe, Ni, Mn, Co, Mg, and Al present in the batteries. The alkali metal Li has not generally been recovered, as its high reactivity makes it difficult to separate from scrap batteries and it is available in sufficient quantities and at low cost from natural deposits. Extracting Li from used LIBs over long periods of time simply seemed uneconomical.

[0006] However, there is currently growing social and economic pressure to recover lithium from used LIBs. To make this idea a reality, it is necessary to supply LIB producers with recycled lithium of acceptable quality so that the manufacturing process for LIBs from recycled lithium is no different from that using mined virgin lithium. It goes without saying that there must be no adverse effects on battery quality. Therefore, recycled lithium, especially in the form of LiOH, must meet very strict specifications regarding purity. Furthermore, the process for recovering lithium from old batteries must be as energy-efficient as possible. The process should also use as little water as possible.

[0007] Known processes for recovering lithium from old batteries are collated below: Pankaj K.Choubey et al.:Advance review on the exploitation of the prominent energy-storage element Lithium.Part II:From sea water and spent lithium ion batteries(LIBs),Minerals Engineering,volume 110,2017,pages 104-121 DOI:10.1016 / j.mineng.2017.04.008. The technique referred to simply as "LISM" in the above review article is the electrolysis of Li-containing water in the presence of what is known as a LiSICon membrane.

[0008] LiSICon stands for Lithium Superionic Conductor. It is a type of inorganic glass-ceramic material that is an electrical insulator, but at the same time has intrinsic conductivity for Li ions. The transport mechanism of Li comes from the crystalline structure of the material. Li ions, simply put, "pass through" the crystal. Commercially available LiSICon materials include lithium aluminum titanium phosphate (LATP), lithium aluminum titanium silicon phosphate (LATSP), lithium aluminum germanium phosphate (LAGP), and lithium lanthanum titanium oxide (LLTO). These materials were originally developed as solid electrolytes for LIBs. An overview of the transport mechanism of LiSICons, their crystalline structures, and production is given below: Palakkathodi Kammampata et al.: Cruising in ceramics-discovering new structures for all-solid-state batteries-fundamentals, materials, and performances.Ionics 24,639-660(2018)DOI:10.1007 / s11581-017-2372-7 Yedukondalu Meesala et al.:Recent Advancements in Li-Ion Conductors for All-Solid-State Li-Ion Batteries.ACS Energy Lett.2017,2,12,2734-2751 DOI:10.1021 / acsenergylett.7b00849 A particular LiSICon stoichiometry is described by: Sofia Saffirio et al.Li 1.4 Al 0.4 Ge 0.4 Ti 1.4(PO4)3promising NASICON-structured glass-ceramic electrolyte for all-solid-state Li-based batteries:Unravelling the effect of diboron trioxide,Journal of the European Ceramic Society,volume 42,issue 3,2022,pages 1023-1032 DOI 10.1016 / j.jeurceramsoc.2021.11.014. Eongyu Yi et al.Materials that can replace liquid electrolytes in Li batteries:Superionic conductivities in Li 1.7 Al 0.3 Ti 1.7 Si 0.4 P 2.6 O 12 .Processing combustion synthesized nanopowders to free standing thin films.Journal of Power Sources,volume 269,2014,pages 577-588,DOI 10.1016 / j.jpowsour.2014.07.029. Their selective conductivity for Li ions means that LiSICon materials can be used as membranes to separate Li from Li-containing mixtures. Li must be present in the mixture in ionic form, for example, as a Li salt dissolved in water. The driving force required to force the Li ions through the LiSICon membrane is a voltage. For this purpose, an electrochemical cell is constructed containing two electrodes and a LiSICon membrane that divides the cell into two compartments. Each compartment contains an electrode. The compartments are called anodes or cathodes, depending on the polarity of the electrodes present in each compartment. A voltage is applied to the electrodes, and the anion compartment is filled with Li-containing water as the anolyte. The cathode compartment is filled with water as the catholyte. The membrane allows Li cations to pass to the cathode. Thus, the water in the cathode compartment (catholyte) is enriched with Li, while the water on the anode side (anolyte) is depleted of Li. This process is called membrane electrolysis.

[0009] Membrane electrolysis processes for the extraction of lithium using LiSICon membranes have already been described in the prior art.

[0010] For example, Zhen Li et al. describe a process that uses weakly lithium-containing water from the Red Sea as a raw material: Zhen Li et al.:Continuous electrical pumping membrane process for seawater lithium mining.Energy Environ.Sci.,2021,14,3152 DOI:10.1039 / d1ee00354b The Zhen Li research group uses LLTO as a membrane. The target product to be separated is lithium phosphate (Li3PO4), which is suitable for producing lithium iron phosphate (LFP) batteries. LIBs with different cathode materials, such as nickel manganese cobalt (NMC) or lithium manganese oxide (NMO), cannot be directly produced using it.

[0011] Yang et al. have attempted to directly extract metallic lithium from seawater using solar power, a LAGP membrane, and copper foil.

[0012] Sixie Yang et al.: Lithium Metal Extraction from Seawater.Joule,volume 2,issue 9,2018,pages 1648-1651,DOI 10.1016 / j.joule.2018.07.006. US Patent Application Publication No. 2016 / 0201163 describes the separation of Li ions from saltwater, such as seawater, using LiSICon membranes. The proposed membrane materials are specifically LiN, Li 10 GeP2S 12 , La x Li y TiO2, and Li 1+x+y Al x (Ti,Ge) 2-x Si y P 3-y O 12 The target product is lithium carbonate (Li2CO3).

[0013] WO 2019055730 also relates to the separation of lithium using LiSICon membranes. LLTO, LAGP, and LATP are specifically mentioned. The LiSICon material can be applied to a support structure. The chemical nature of the support structure is not described in detail. Similarly, there is little information about how the LiSICon should be applied to the support structure. The target product to be separated is Li ions.

[0014] U.S. Patent No. 9,222,148 also discloses the separation of lithium hydroxide by electrolysis on a LiSICon membrane, resulting in the precipitation of lithium hydroxide hydrate. A drawback of this process is that it requires an energy-intensive evaporation step to precipitate the lithium hydroxide.

[0015] US Patent Application Publication No. 20120103826 describes the electrodialytic separation of lithium hydroxide from contaminated streams using LiSICon membranes. To achieve high purity, LiOH is precipitated from brine. This takes advantage of the fact that the solubility of LiOH in water is lower than that of the foreign salt. The precipitate is then redissolved and introduced into the electrodialysis cell. The LiOH concentration in the electrodialysis cell's catholyte is not specified in US Patent Application Publication No. 20120103826. The catholyte is diluted with water. The disadvantages of this process are the need for laborious crystallization prior to electrolysis and the loss of heat of crystallization as a result of the redissolution of the precipitate. Therefore, this process is technically laborious and energy-intensive.

[0016] In addition to the use of ceramic LiSICon membranes, electrolytic processes for the separation of lithium operating with organic ion exchange membranes have also been disclosed.

[0017] For example, EP 3805428 A1 describes the electrolytic production of lithium hydroxide. Similar to electrolysis, the electrochemical conversion of lithium to lithium hydroxide is also operated. To obtain the necessary reactants, water undergoes simultaneous electrochemical splitting. This is carried out using a bipolar three-compartment cell equipped with ion-exchange membranes. Commercially available ion-exchange membranes are used: Asahi® AVV, Nafion® 902, Fumatech® FAB, Fumatech® FKB, and Neosepta® CMB. The chemical nature of these ion-exchange membranes is not disclosed in EP 3805428 A1, but they are likely organic membrane materials. The three-compartment cell operates in an acidic medium. The feed uses water containing Li salts, particularly lithium sulfate (LiSO4) or lithium chloride (LiCl).

[0018] A two-stage electrodialysis / electrolysis production of lithium hydroxide from aqueous lithium sulfate and / or lithium bisulfate with simultaneous water splitting is disclosed in U.S. Pat. No. 10,036,094. The first stage uses an electrochemical cell with two compartments, and the second stage uses a three-compartment cell. The cells are equipped with ion-exchange membranes. The chemical composition of the ion-exchange membranes is not given. The following commercially available membranes are mentioned: Fumatech® FAB, Astom® ACM, Asahi® MV, Nafion® 324, and Astom® AHA. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] US Patent Application Publication No. 2016 / 0201163 [Patent Document 2] International Publication No. 2019055730 [Patent Document 3] U.S. Patent No. 9,222,148 [Patent Document 4] US Patent Application Publication No. 20120103826 [Patent Document 5] European Patent Application Publication No. 3805428 [Patent Document 6] U.S. Patent No. 10,036,094 [Non-patent literature]

[0020] [Non-Patent Document 1] Wietelmann, U. and Steinbild, M. (2014). Lithium and Lithium Compounds. In Ullmann's Encyclopedia of Industrial Chemistry, (ed.). DOI:10.1002 / 14356007.a15_393.pub2 [Non-patent document 2] Pankaj K.Choubey et al.:Advanced review on the exploitation of the prominent energy-storage element Lithium DOI:10.1016 / j.mining.2017.04.008.

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[0021] The main drawback of polymer membranes is their permeability to water, which leads to dilution of the anolyte with water from the catholyte. Dehydration of the target product is then necessary, which consumes thermal energy or limits the plant location to areas with sufficient sunlight.

[0022] A further fundamental drawback of organic ion exchange membranes, besides their water permeability, is that they have lower ion selectivity than inorganic LiSICon materials: they + Not only Na + As well as the purity of the target product, the electrical efficiency of the process is also reduced as a result: if electrolysis is carried out using a non-ion selective membrane, the unwanted Na + The transport of Na to the second compartment also consumes valuable electrical energy. + is converted to undesired by-products through unintended electrochemical processes, reducing the energy efficiency of the process based on the yield of the target product, Li.

[0023] Finally, the organic film is 2+ and Ca 2+ Over time, these cations poison the membrane, thereby limiting the useful life of organic ion exchange membranes.

[0024] Glass-ceramic LiSICon materials promise better ion selectivity. However, the stability of LiSICon membranes against impurities remains a critical issue for industrial implementation. For example, Li ions generated in the reprocessing of spent LIBs are also present. + The contained water is especially Na + and K. +These cations appear to occupy defects in the crystal structure, thereby allowing Li ions to pass through the membrane. + This virtually stops cation transport. The useful life of the electrochemical cell then expires. The high cost of LiSICon materials means that recycling Li from LIBs is uneconomical if the membrane has a short useful life. Furthermore, brine from Li-salt lakes has a naturally high sodium content, making it impossible to contact known LiSICon membranes. Therefore, lithium from the lakes must be dissolved and then recrystallized via a stepwise process that requires energy-intensive thermal separation and / or large amounts of water. While water can be evaporated here by solar radiation, water to dissolve LiCl is scarce in the South American desert. Therefore, this route is highly problematic there.

[0025] Another practical problem is the high specific electrical resistivity of LiSICon materials. This results in electrochemical cells with high ohmic internal resistance, which means that the process has correspondingly high electrical energy requirements. To reduce this, the membrane could theoretically be made thinner. However, a thinner material would have a shorter lifetime in aggressive environments.

[0026] In light of this prior art, the problem addressed by the present invention is to identify a highly energy-efficient lithium hydroxide production process. The process should operate without using thermal energy, in particular. As a raw material, the process should be capable of processing the Li-containing water produced when used lithium-ion batteries are digested. The LiOH produced by the process should be of sufficiently high purity that it can be used directly in the production of new LIBs. The process should achieve high throughput and have low space requirements so that it can be combined with existing processes for the reprocessing of used LIBs or the production of new LIBs to form a closed, continuous production cycle. Finally, the process should require as little freshwater as possible and produce little wastewater. [Means for solving the problem]

[0027] This problem is solved by the process according to claim 1.

[0028] Accordingly, the present invention provides a process for producing hydrogen and lithium hydroxide, comprising: a) providing a feed containing at least water, Li ions, and also impurities, wherein the concentration of Li ions in the feed, C F is at least 200 ppm (by weight) or between 500 ppm (by weight) and 140,000 ppm (by weight), in each case based on the total weight of the feed; b) providing a lean working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration C of lithium hydroxide in the lean working medium is M0 is at least 50 ppm (by weight) based on the total weight of the lean working medium; c) providing at least one electrochemical cell, the electrochemical cell having the following characteristics: i) the electrochemical cell includes a first compartment having an anode disposed therein; ii) the electrochemical cell includes a second compartment having a cathode disposed therein; iii) the electrochemical cell includes a membrane separating a first membrane from a second membrane, the membrane having an area A; iv) the membrane comprises an inorganic material that is conductive to Li ions and electrically insulating; d) providing at least one voltage source connected to the anode via a first electrical lead and connected to the cathode via a second electrical lead; e) filling the first compartment with a supply; f) filling the second compartment with a lean working medium; g) charging the electrochemical cell with a voltage U drawn from a voltage source so that a current I flows between the anode and the cathode, the ratio Q of the current intensity of the current I to the area A of the membrane being 100 A / m 2 ~500A / m 2 or 150A / m 2 ~350A / m 2 the charging step; h) withdrawing wastewater from the first compartment, the wastewater containing at least water, dissolved Li salts therein, oxygen, and also impurities, wherein the concentration of Li ions in the wastewater, C W is the concentration of Li ions in the feed based on the total weight of the feed, C, based on the total weight of the wastewater. F Lower than, pull out step; i) withdrawing a rich working medium comprising water, hydrogen, and lithium hydroxide from the second compartment, wherein the concentration of lithium hydroxide in the rich working medium, C, is determined based on the total weight of the rich working medium. M1 is the concentration of lithium hydroxide in the poor working medium, C M0 The concentration of lithium hydroxide in the rich working medium, based on the total weight of the rich working medium, is higher than C M1 At temperature T M1 The solubility of lithium hydroxide in water at temperature T M1 refers to the temperature of the working medium when withdrawn from the second compartment.

[0029] The process according to the present invention is an electrolytic membrane process operated using a LiSICon membrane. [Brief explanation of the drawings]

[0030] [Figure 1] The functional principle of simultaneous Li+ membrane electrolysis and water electrolysis in an electrochemical cell using a LiSICon membrane is presented. [Figure 2] 1 illustrates the functional principle of recirculation between the electrochemical cell and the separation device. [Figure 3] Conductivity as a function of concentration of LiOH solution (25 °C). [Figure 4] Experiment results in graphical form. [Figure 5] Results of replicate experiments in graphical form. DETAILED DESCRIPTION OF THE INVENTION

[0031] An important aspect of the process according to the invention is that the selective separation of lithium by the membrane and the electrolysis of water occur simultaneously within the cell. In water electrolysis, water (H2O) is electrochemically split into H2 and O2. At the cathode, OH - However, OH - Anions cannot pass through the LiSICon membrane and reach the cathode compartment. + At the anode, oxygen and H + is formed.

[0032] Thus, the simultaneous operation of Li+ membrane separation and water electrolysis in an electrochemical cell using a LiSICon membrane results in the direct formation of lithium hydroxide (LiOH) and molecular hydrogen (H2). Both dissolve in water. Water containing LiOH and H2 is withdrawn from the cathode compartment of the cell. LiOH is separated from the water. This allows for the selective migration of lithium ions through the membrane to extract LiOH of sufficient purity for use in battery production.

[0033] The co-produced hydrogen can be collected and used in the hydrogen economy. If the electrochemical cell is operated with green electricity, the process also has a small CO2 footprint.

[0034] The feed required for combined Li separation and water electrolysis is Li + This water contains cations. Such water can be produced during the reprocessing of spent LIBs, or Li brines from natural deposits can be used.

[0035] A key aspect of the process is that the electrolysis is operated up to and beyond the precipitation limit of lithium hydroxide: this is the concentration of lithium hydroxide in the rich working medium, C, based on the total weight of the rich working medium. M1 This means that the solubility of lithium hydroxide in water is greater than that of lithium hydroxide. Therefore, lithium hydroxide can precipitate as a solid in the catholyte if the necessary crystal nuclei are present. Since these are always present in the form of small amounts of impurities, at least a portion of the LiOH precipitates as a solid in the rich working medium (catholyte).

[0036] The point at which lithium hydroxide in the catholyte precipitates as a solid depends on the operating conditions of the cell and the presence of crystalline nuclei: lithium hydroxide may precipitate as a solid already in the second compartment, or it may precipitate only immediately after withdrawal of the rich working medium, i.e., outside the cell. According to the present invention, the rich working medium withdrawn from the second compartment always contains solid lithium hydroxide.

[0037] The rich working media preferably contains solid lithium hydroxide when withdrawn from the second compartment.

[0038] Solid lithium hydroxide optimally refers to lithium hydroxide in crystalline form. Because lithium hydroxide crystals can also intercalate water, lithium hydroxide may exist in gel form. In the gel, lithium hydroxide forms a solid phase and water forms a liquid phase. Gel formation is also determined by the remaining impurities in the second compartment. This means that the precipitation of gel-form lithium hydroxide depends on the thermodynamic conditions in the second compartment and the concentrations of lithium hydroxide and impurities therein. Therefore, a gel containing solid lithium hydroxide and liquid water is also considered a solid for purposes of this invention. Therefore, the term "solid" encompasses both crystalline forms and gels.

[0039] The precipitation limit of lithium hydroxide in the second compartment is then determined by the concentration C of lithium hydroxide in the rich working medium based on the total weight of the rich working medium. M1 At temperature T M1This is achieved when the solubility of lithium hydroxide in water at temperature T is greater than or equal to the solubility of lithium hydroxide in water at temperature T M1 refers to the temperature of the working medium when it is withdrawn from the second compartment.

[0040] This is because, like most water-soluble inorganic solids, the solubility of lithium hydroxide in water is temperature dependent. Therefore, the exact location of the precipitation limit depends on the temperature of the rich working medium. The present invention is based on the temperature T at which the rich working medium is withdrawn from the second compartment. M1 Consider the temperature T M1 The optimum temperature is between 20°C and 60°C. This temperature corresponds in the simplest case to the operating temperature of the electrochemical cell. However, it is possible to operate the cell at a higher temperature and to increase the temperature of the working medium to T just before or during withdrawal. M1 However, this does not always make sense energetically.

[0041] The solubility of lithium hydroxide in water actually depends on the purity of the water: if it contains impurities, these act as nuclei and promote the precipitation of lithium hydroxide.

[0042] Finally, it also makes a difference whether the lithium hydroxide concentration is calculated in its anhydrous (LiOH) form or its monohydrate (LiOH·H2O) form.

[0043] All this clearly leads to reported solubilities of lithium hydroxide that are inconsistent in either the scientific literature or patent applications.

[0044] A comprehensive overview of the solubility of lithium hydroxide in water is presented by Monnin and Dubois: Christophe Monnin and Michel Dubois:Thermodynamics of the LiOH+H2O System.Chem.Eng.Data 2005,50,4,1109-1113 DOI 10.1021 / je0495482 Furthermore, Monnin and Dubois mathematically interpolated values ​​known from the literature.

[0045] The solubility of lithium hydroxide in water at relevant temperatures according to various authors is given in Table 1:

[0046] [Table 1]

[0047] *Values ​​by Ullmann and KirkOthmer calculated as monohydrate, remaining values ​​calculated as anhydrous.

[0048] The values ​​shown in Table 1 are derived from the following literature sources: Dittmar:DOI https: / / doi.org / 10.1016 / 0016-0032(89)90312-8 D1:US 2012103826 A1 S&M:DOI https: / / doi.org / 10.1021 / je60015a018 Xie et al.: DOI https: / / doi.org / 10.1016 / j.seppur.2023.123972 M&D:DOI https: / / doi.org / 10.1021 / je0495482 KirkOthmer:DOI https: / / doi.org / 10.1002 / 0471238961.1209200811011309.a01.pub2 Ullmann:DOI https: / / doi.org / 10.1002 / 14356007.a15_393.pub2 T 20℃~60℃ M1 With respect to the desired temperature range, the concentration of lithium hydroxide in the rich working medium, C, based on the total weight of the rich working medium M1is preferably greater than 0.1276 kg / kg (which is the lowest reported solubility of LiOH in water at a temperature of 333.15 K = 60 °C, according to Table 1). Preferably, the concentration C of lithium hydroxide in the rich working medium is 0.1276 kg / kg, based on the total weight of the rich working medium. M1 is greater than 0.138 kg / kg or greater than 0.146 kg / kg. These values ​​are understood to be calculated as anhydrous LiOH. If the concentration is determined as lithium hydroxide monohydrate, the concentration C of lithium hydroxide in the rich working medium is M1 should be greater than 0.23 kg / kg or greater than 0.256 kg / kg.

[0049] On the other hand, the concentration of lithium hydroxide in the lean working medium, C, based on the total weight of the lean working medium M0 The LiOH concentration should be less than 12.8% (by weight). This ensures that LiOH is not introduced into the second compartment already in solid form. The lower limit for the LiOH concentration in the lean working medium is 50 ppm. Otherwise, the reaction will not start or proceed.

[0050] In connection with the discussion of the solubility of lithium hydroxide in water, it should be emphasized that the cell does not need to be operated exactly at the solubility limit. It is assumed that the cell will be operated above the precipitation limit, especially since a large amount of LiOH will precipitate as a solid. M1 The upper limit of C is determined by the pumpability of the rich working medium: if the rich working medium contains too much solid lithium hydroxide, it is no longer possible to pump it out of the second compartment. Therefore, the LiOH concentrations listed in Table 1 are used to calculate the C M1 The upper limit corresponds to the lower limit of C. The upper limit results from the equipment setup of the plant in which the process according to the invention is carried out. In particular, the structural design of the conveying means leading to the withdrawal of the rich working medium from the second compartment and its transport to the downstream separation device is important for the upper limit. In the realization of the process according to the invention, a separation device is used to separate the LiOH from the rich working medium. Bottlenecks in the conveying means and in the cells and pipe connections can become clogged with the crystallization product, thus increasing the C M1 It also defines the technically manageable upper limit of

[0051] Since inorganic membranes are not sensitive to foreign ions, the feed can contain anions selected from the group consisting of sulfate, carbonate, hydroxide and chloride.

[0052] In addition to the anions mentioned, the feed may also contain impurities in the form of compounds of the following elements: B, Na, Mg, Al, Si, K, Ca, Mn, Fe, Co, Ni, Cu, and C. The listed alkali and alkaline earth metals are elements found with lithium in natural deposits, while the other metals mentioned are used as conductive or cathode materials in LIBs and are consequently present in the feed obtained from the reprocessing of spent LIBs. Carbon is also found in the recyclable material stream from the reprocessing of spent LIBs and originates from polymeric components of the battery cells, such as films, separators, adhesives, or sealants.

[0053] According to the present invention, a membrane containing inorganic materials is used. Therefore, the required ion selectivity is achieved differently than in the case of polymeric membranes. The membrane is preferably made entirely of inorganic materials. Composite membranes that contain inorganic materials only as a coating on a support material or in which inorganic materials are dispersed in different types of matrix materials have proven to be an incorrect approach.

[0054] For the process to work, the inorganic material must conduct Li ions and simultaneously act as an electrical insulator. The specific conductivity g (electrical conductivity) of the electrons is 10 -7 Less than S / cm (10 -9 S / m), or 10 -12 Less than S / m or 10 -16 It must be less than S / m.

[0055] Therefore, from the standpoint of electronic conduction, inorganic materials are classified as non-conductors.

[0056] The specific conductivity s of inorganic materials for Li-ions is at least 1*10 at a temperature of 23°C. -5S / m or at least 5*10 -5 S / m or at least 10*10 -5 S / m and 100*10 -5 The Li conductivity of the material is measured by impedance spectroscopy. This measurement is performed as follows: The measurement setup comprises two cylindrical electrodes between which the sample is placed. A weight is placed on the sample to ensure optimal contact with the electrodes and a reproducible contact pressure.

[0057] A potentiostat (Zahner-Elektrik I. Zahner-Schiller GmbH & Co. KG, Kronach-Gundelsdorf, Germany) is connected to the electrodes and controlled via Thales software (Zahner). Measurements are performed in the frequency range of 1 Hz to 4 MHz and at an amplitude of 5 mV using samples polished and sputtered onto a thin conductive gold layer.

[0058] The measurement results are presented in the form of a Nyquist plot and evaluated using analytical software (Zahner). The electrical resistance is read at the maximum value of the Nyquist plot curve. The specific ionic conductivity σ [mS / cm] is then calculated using the formula σ = (h 10 4 ) / (R π / 4 d 2 ) where h is the height of the sample (mm), R is the measured electrical resistance (Ω), and d is the diameter of the sample (mm).

[0059] It is preferred to use LiSICon as the inorganic material. LiSICon material is a glass-ceramic material that conducts lithium ions and simultaneously acts as an electrical insulator. In principle, all known LiSICon materials can be used as inorganic materials for the purposes of the present invention. Known LiSICon materials meet the above-specified requirements for both the electrical conductivity and ionic conductivity of inorganic materials.

[0060] For example, the LiSICon material lithium aluminum titanium phosphate (LATP) can be used. Thus, in one variant of the invention, the inorganic material is a compound of the following stoichiometry:

[0061] [ka]

[0062] [wherein 0.1≦x≦0.3, preferably x=0.3].

[0063] Alternatively, the LiSICon material lithium aluminum titanium silicon phosphate (LATSP) can be used. Thus, in one variant of the invention, the inorganic material is a compound of the following stoichiometry:

[0064] [ka]

[0065] [wherein 0.1≦x≦0.3 and 0.2≦y≦0].

[0066] In a particularly preferred development of the invention, LATSPs are used which additionally contain germanium. LAGTSPs are available, for example, under the product name LICGC® AG01 from OHARA GmbH, Hofheim, Germany.

[0067] The stoichiometry of LAGTSP is as follows:

[0068] [ka]

[0069] [Where 0≦x≦1 and 0≦y≦1 and 0≦n≦1].

[0070] Alternatively, the LiSICon material lithium aluminum germanium phosphate (LAGP) can be used. Thus, in one variant of the invention, the inorganic material is a compound of the following stoichiometry:

[0071] [ka]

[0072] [wherein x=0 or x=0.2 or x=0.4].

[0073] However, it is particularly preferred to use LiSICon, which is derived from lithium aluminum germanium phosphate (LAGP) but which also contains titanium, and which is called LAGTP.

[0074] Thus, in a preferred variant of the invention, the inorganic material is a compound of the following stoichiometry:

[0075] [ka]

[0076] [wherein 0≦x≦1].

[0077] As an alternative to the above-mentioned phosphates, the oxide LiSICon material lithium lanthanum titanium oxide (LLTO) can be used. Thus, in one variant of the invention, the inorganic material is a compound of the following stoichiometry:

[0078] [ka]

[0079] [wherein 0≦x≦0.16].

[0080] The lithium hydroxide is present in the rich working medium and is withdrawn from the second compartment together with it. To be able to utilize it, it must be separated from the rich working medium. For this purpose, a separation device is provided. Therefore, a preferred development of the invention comprises the following additional process steps: k) providing a separation device; l) Separating the lithium hydroxide from the rich working medium using a separator.

[0081] The process is preferably operated such that the separation unit separates a product having the following composition: Lithium hydroxide: >56.5% (by weight) Water: <43.5% (by weight) Carbon dioxide: <0.35% (by weight) Sulfur dioxide: <0.01% (by weight) Chlorine: <0.002% (by weight) Calcium: <15 ppm (by weight) Iron: <5 ppm (by weight) Sodium: <20 ppm (by weight) Aluminum: <10 ppm (by weight) Chromium: <5 ppm (by weight) Potassium: <10 ppm (by weight) Copper: <5ppm (weight basis) Nickel: <10 ppm (by weight) Silicon: <30 ppm (by weight) Zinc: <10 ppm (by weight) Other substances: <10% (by weight) [Parts by weight total 100% and are based on the total weight of the product.] This kind of product is battery-grade LiOH and can be directly used in the production of LIBs.

[0082] The product separated by the separator contains solid lithium hydroxide. The product preferably meets the above specifications so that it can be directly used as battery-grade LiOH for producing new LIBs. However, the separated product is not pure LiOH. The principle of its formation means that the separated product always contains water, which is trapped in the LiOH crystals (crystal water / internal water). However, the water content of the separated product is less than 43.5% (by weight), thus meeting the battery-grade specifications. At this water content, the separated product is a crystalline solid, not a gel.

[0083] The working medium, from which LiOH has been removed in the separator, is returned to the electrochemical cell as lean working medium, where it is recharged. The working medium is thus recycled in a closed system. The resulting working medium recycles between the second compartment and the separator. Recycling the working medium results in savings in both the freshwater supply and wastewater disposal.

[0084] The lean working medium is completely free of LiOH, but contains a specific minimum concentration of C of about 50 ppm (by weight). M0 It is important to have a constant value of 0.01%. Otherwise, it is impossible to maintain the process in the cell continuously. Therefore, the separator does not completely separate the LiOH present in the rich working medium, leaving a residual concentration in the working medium. The separator preferably separates only the solid LiOH, and does not exceed the initial concentration C. M0 Leave the LiOH dissolved in the working medium as is.

[0085] A preferred development of the invention therefore comprises the following additional process steps: l) separating the lithium hydroxide from the rich working medium using a separator to provide a lean working medium; Including, b) providing a lean working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration C of lithium hydroxide in the lean working medium is M0 is at least 50 ppm (by weight) based on the total weight of the lean working medium, This is done using a separation device.

[0086] To allow for the recirculation of the working medium between the separator and the second compartment, it makes sense to install both devices in the same location. This should be understood as meaning an integrated production facility. The electrochemical cell and the separator are therefore part of an integrated facility. The closed recirculation of the working medium allows the electrochemical cell and the separator to be installed in the same location and operated continuously. The process is preferably integrated directly into an integrated plant, which includes a unit for reprocessing used LIBs and a unit for producing new LIBs. However, it is also possible to simply combine the process with a battery recycling plant and export the resulting LiOH.

[0087] It is also conceivable that the separation device could be located at a different location from the electrochemical cell, but in that case the working medium would have to be transported between the cell and the separation device, which makes little sense from an energy point of view.

[0088] At least the electrochemical cell is preferably operated continuously. This means that there is a constant flow between the two compartments. The first compartment has a continuous flow of feed, resulting in the production of wastewater, while the second compartment has a flow of working medium, which enters as lean working medium and exits as rich working medium. This allows for both higher throughput and continuous removal of membrane-damaging components in the feed and working medium. Therefore, continuous operation is expected to achieve better membrane stability than batch operation.

[0089] Thus, a preferred embodiment of the process comprises at least the process steps: i) withdrawing a rich working medium comprising water, hydrogen, and lithium hydroxide from the second compartment; and l) separating the lithium hydroxide from the rich working medium using a separation device; is expected to be carried out continuously.

[0090] Since LiOH accumulates in solid form in the process according to the present invention, the separation device is preferably designed as a solid separator. Suitable solid separators are filters, hydrocyclones, and sedimentation separators. These devices do not require thermal energy. As a result, the process described herein primarily requires electrical energy to operate the electrochemical cell and secondary electrical energy to transport the material flow. Therefore, the process can preferably be operated with green electricity.

[0091] Drawing Description: The invention will now be described in detail with reference to a process flow diagram, in which: Figure 1 shows the simultaneous Li+ / Li ... + The functional principles of membrane electrolysis and water electrolysis are shown.

[0092] FIG. 2 shows the functional principle of the recirculation between the electrochemical cell and the separation device.

[0093] The electrochemical cell 0 required to carry out the process is shown in Figure 1. It comprises a first compartment 1 and a second compartment 2. The two compartments 1 and 2 are separated from each other by a membrane 3. An anode 4 is located in the first compartment 1. A cathode 5 is located in the second compartment 2. Thus, the first compartment 1 can be referred to as the anode compartment, and the second compartment 2 can be referred to as the cathode compartment.

[0094] A first electrical lead 6 connects the anode 4 to a voltage source 7. A second electrical lead 8 connects the cathode 5 to the voltage source 7. The selected polarity of the voltage source 7 is such that the positive terminal of the voltage source 7 is connected to the anode 4 and the negative terminal of the voltage source 7 is connected to the cathode 5.

[0095] An electric current I flows through two electrical leads 6 and 8 via a voltage source 7. There is no electrical short circuit between the two electrodes 4 and 5 through the membrane 3, as the membrane 3 acts as an electrical insulator.

[0096] The membrane 3 is a flat sheet membrane made entirely of LiSICon material. The anode 4 is a flat metal plate made of titanium, niobium, or tantalum. The cathode 5 is also a flat metal plate made of titanium or nickel. In the simplest case, a stainless steel plate is used as the cathode. The anode 4, cathode 5, and membrane 3 all have the same shape and can be rectangular or circular. This is not clear from the side view in Figure 1. Instead of metal plates, it is also possible to use expanded metal, mesh, or netting of a certain material as electrodes.

[0097] The electrochemical cell 0 has an active area A corresponding to the surface area of ​​the membrane 3 , the anode 4 and the cathode 5 .

[0098] During operation, the first compartment 1 is filled with a feed 10. The feed 10 is an aqueous solution containing Li+ ions. From an electrochemical point of view, the feed 10 is considered an anolyte.

[0099] Feed 10 may be a Li leachate from natural deposits or a material stream resulting from the reprocessing of spent LIBs. The concentration of Li+ cations in feed 10 (with formula symbol c F ) should be at least 200 ppm (by weight) based on the total mass of the feed. Seawater has a low Li concentration and must first be concentrated before use in the process. Feed 10 also contains anions such as sulfate or chloride. Feed 10 also contains impurities. The anions and impurities are not shown in Figure 1. The main component of feed 10 is water, HO.

[0100] The second compartment is filled with lean working media 12. The lean working media 12 is Li + Cation concentration C M0 The concentration of water is low. M0is at least 50 ppm (by weight) based on the total mass of the lean working medium 12. From an electrochemical standpoint, the lean working medium 12 is considered to be the catholyte.

[0101] The electrochemical cell 0 is also charged with a voltage U drawn from a voltage source 7. This has the following effects:

[0102] First, water electrolysis occurs, where water (H2O) is electrochemically split into hydrogen (H2) and oxygen (O2). At the cathode 5, OH - However, OH - The anions cannot pass through the membrane 3 and are transported to the cathode compartment 2 via the Li + At the anode 4, oxygen and H + is formed.

[0103] The formation of LiOH in the cathode compartment 2 is sustained by the migration of Li+ cations from the feed 10 to the cathode 5, driven by the voltage U. They cross the membrane 3 due to the membrane's Li-ion conductivity and accumulate in the working medium (membrane electrolysis). This forms a rich working medium 13 that is withdrawn from the second compartment 2. The Li+ ion concentration in the rich working medium 13 is higher than in the lean working medium 12, so c M1 >c M0 is.

[0104] Therefore, in electrochemical cells, water electrolysis, Li + The membrane electrolysis and synthesis of LiOH proceed simultaneously.

[0105] Thus, the simultaneous operation of Li+ membrane electrolysis and water electrolysis in the electrochemical cell results in the direct formation of lithium hydroxide LiOH and molecular hydrogen H2. The hydrogen is at least partially dissolved; it may be present in the form of gas bubbles. According to the present invention, lithium hydroxide is concentrated beyond its solubility. This means that lithium hydroxide is at least partially present in solid form in the rich working medium 13.

[0106] Depending on the temperature and the presence of crystal nuclei, LiOH precipitates already in the second compartment 2 or immediately after withdrawing the rich working medium 13. Impurities typically act as crystal nuclei.

[0107] As a result of membrane electrolysis, the feed 10 becomes depleted in Li+, producing wastewater 14. W <c F Here, the formula symbol c W represents the Li ion concentration in the wastewater 14 based on the total mass of the wastewater 14. F represents the concentration of Li ions in the feed 10 based on the total mass of the feed 10.

[0108] FIG. 2 shows how LiOH is extracted as the target product 15 from the rich working medium 13.

[0109] For this purpose, a separation device 16 is provided to which the rich working medium 13 is conveyed. The separation device 16 separates the target product 15, which has a particularly high concentration of LiOH, from the rich working medium 13. The target product also contains water and impurities, depending on the desired specifications of the target product.

[0110] Because the rich working medium 13 contains LiOH in solid form, the separation device 16 is preferably a solid separator, such as a filter. The solid LiOH is filtered out of the rich working medium 13 and corresponds to the actual product of the process.

[0111] The LiOH-depleted effluent stream from the separator 16 is recycled to the second compartment 2 of the electrochemical cell 0 as lean working medium 12 .

[0112] As mentioned above, the poor working medium 12 is required to have a specific LiOH concentration C so that the process in the electrochemical cell 0 can be initiated in the desired manner due to the low initial resistance. M0 It is necessary to have a concentration c M0 The desired concentration C must be at least 50 ppm (by weight) based on the total mass of the lean working medium 12. M0To ensure this, the separator 16 operates in such a way that not all of the LiOH is separated from the rich working medium 13. This is particularly easy when using a solid separator, as the dissolved portion of the LiOH is left in the working medium and can be recycled into the second compartment 2 at the required starting concentration of above 50 ppm.

[0113] In addition to lithium hydroxide LiOH, the process also produces H2, which is at least partially dissolved in the rich working medium 13 and is withdrawn from the second compartment 2 together with LiOH.

[0114] Since hydrogen H2 is easily degassed from water, it does not require much effort to remove it from the working medium. Only when hydrogen H2 is utilized as the second target product, a corresponding second separation device is provided (not shown) from which hydrogen can be obtained separately with suitable quality / purity.

[0115] The water HO present in the rich working medium 13 is recycled as completely as possible as the lean working medium 12. Only the water (of crystallization) present in the target product 15 is lost from the process; this must be replenished to the lean working medium 12 as needed (not shown). The water in the feed 10 is not finally recycled between the second compartment 2 and the separation device 16 because the membrane 3 is impermeable to water.

[0116] experiment: The effects achieved by the present invention will now be explained with reference to experiments.

[0117] To carry out electrolysis, the electrolysis cell is first assembled and the anolyte and catholyte containers are connected, with care being taken to ensure that the inlet and outlet flows are connected on the same side in each case.

[0118] The anodes and cathodes used were in each case circular disks with a diameter of 19.5 mm and a thickness of 1 mm. The materials were in each case titanium expanded metal plates coated on both sides with IrTi mixed oxide (12 g Ir / m, 1 AF D 1.5 mm) from Metakem GmbH, 61250 Usingen, Germany.

[0119] The sampled membrane was also a circular disk with a diameter of about 25 mm. The thickness of the membrane was about 1 mm. The material of the sampled membrane was LATSP, i.e., LICGC® PW01, manufactured by Ohara GmbH, Hofheim, Germany.

[0120] The electrolysis and corresponding storage vessels are blanketed with nitrogen throughout the process to prevent the formation of lithium carbonate. Each cell has a separate anolyte container and a separate catholyte container. Each container is filled with approximately 1 kg of liquid. The exact mass is determined by reweighing. In all experiments, the catholyte was always a 5 mmol / L LiOH solution (equivalent to 120 ppm LiOH by weight). The anolyte was in each case a lithium salt solution of various lithium salts at various concentrations. The starting concentration was 1.0 mol / L LiOH in each case. The exact concentrations changed during the course of the experiment and are also indicated in the experimental diagrams.

[0121] The experiment begins when the pump is switched on and the desired voltage is applied. The maximum flow rate is 900 mL / min. Samples are collected every 30 minutes, or at longer intervals if agreed. The first 3 mL of sample collected is discarded. For each sample collected, the output is recorded in each case and the pH and conductivity of the sample are determined. The sample is then returned to a suitable container, keeping the volume substantially constant.

[0122] At the end of the experiment, the vessel is emptied and all leads and membranes are rinsed with demineralized water. The cell is disassembled, the membrane is photographed, and SEM images of the catholyte and anolyte sides are recorded to document any damage or changes to the membrane.

[0123] Membrane performance is expressed as permeability (g Li*mm / m 2 *h) and permeance (g Li / m 2 *h). Permeance indicates how much mass of lithium is transported through the membrane per unit membrane area and unit time. Permeance also takes membrane thickness into account, and therefore makes it possible to compare different membrane types with different thicknesses. Very thin membranes can tolerate very high permeance, but if concentration polarization effects are present in the membrane cell, permeance gives an inaccurate picture, so both are necessary for a comprehensive description of performance. When membrane thickness is taken into account, transport is no longer limited by the membrane and therefore no longer serves a useful purpose.

[0124] All measurements shown in the examples are subject to a measurement error of approximately ±10% due to imprecision in positioning the electrodes relative to each other, in determining the thickness of the film sample, and in determining concentration by conductivity measurements.

[0125] The concentration was determined in-line by measuring the conductivity, which was then converted to concentration via the calibration curve shown in Figure 3.

[0126] FIG. 3 shows the conductivity as a function of concentration of LiOH solution (25° C.).

[0127] However, this means that at concentrations above approximately 10% LiOH, it is nearly impossible to accurately monitor the actual concentration by conductivity measurements.

[0128] First experiment: The first experiments, attempting to increase the concentration above 10% LiOH, are summarized in Table 2 and Figure 4. Here, the reduced accuracy of the concentration determination due to the conductivity determination had to be considered.

[0129] [Table 2]

[0130] Figure 4 shows the results of the experiment in graphical form.

[0131] The jagged progression of anolyte conductivity evident in Figure 4 is due to periodic regeneration of the anolyte when it reached a concentration approximately less than half of the starting concentration. After approximately 100 hours, the cell was leaking, and the catholyte had to be replaced. This caused a very rapid drop in concentration, and therefore in the conductivity of the catholyte solution. This experiment demonstrated that, using this operating procedure, the lithium hydroxide concentration could be increased well above the starting concentration of the anolyte. Because differential evaluation of the lithium hydroxide concentration was not possible, the experiment was terminated after approximately 500 hours of run time, at a lithium hydroxide content of approximately 9%. The catholyte temperature was 27°C, and no solid lithium hydroxide had formed.

[0132] Second experiment: A repeat experiment using the same formulation as in Table 2 gave the following results: FIG. 5 shows the results of replicate experiments in graphical form.

[0133] The periodic regeneration of the anolyte solution is also evident in the jagged course of the anolyte conductivity measurements in Figure 5. The catholyte conductivity increases to a limit of approximately 395-400 mS / cm over approximately 1000 hours, which is due to the solubility and electrical properties of the lithium hydroxide solution at a temperature of approximately 25°C. As already mentioned above, the exact concentration cannot be determined by conductivity, so samples were taken after approximately 1010 hours of operation and the lithium hydroxide content was determined gravimetrically.

[0134] The temperature of the anolyte and catholyte was then increased to 40°C and electrolysis continued. The temperature correction specified by the manufacturer of the measuring device was applied to the conductivity determination. At this high temperature, the conductivity (with temperature correction) did not increase further and therefore remained around 400 mS / cm.

[0135] After 48 hours of continued electrolysis operation, the saturation limit of lithium hydroxide at a temperature of 40° C. should be reached. Therefore, a further sample was taken from the catholyte circulation and its lithium hydroxide content determined gravimetrically.

[0136] The temperature of both circuits was then increased to 60°C and electrolysis continued. After approximately another 90 hours, the saturation concentration at this temperature should again be reached, which should be confirmed by sampling and gravimetric determination of the solids content. The temperature was finally increased to 80°C and operation continued to the desired saturation concentration over a planned period of approximately 110 hours, when the measuring device developed a leak after approximately 60 hours, preventing the experiment from being terminated. Samples were taken to determine the solids content.

[0137] The remaining catholyte was then drained, cooled to room temperature under a nitrogen atmosphere, and left to stand for a period of time to allow some of the lithium hydroxide to settle as a white deposit from the solution, now held at 20° C. All work to determine concentrations was carried out under a nitrogen blanket with the exclusion of carbon dioxide.

[0138] The results of the individual content determinations are summarized in Table 3. They reflect the amount of lithium hydroxide in solution at the end of each temperature level determined by sampling. The average permeability is calculated from the determined content, the electrolysis time, and the area of ​​the membrane used.

[0139] [Table 3]

[0140] *LiOH solubility taken from Table 1.

[0141] From Table 3, it can be seen that the LiOH content exceeded the saturation limit by about 0.1–0.3%. Upon cooling, solid LiOH·H2O was formed.

[0142] Conclusion: The experiments demonstrate that it is possible to carry out the process above the solubility limit of LiOH in the cell, which means that solid LiOH can be produced in an electrochemical cell alone. [Explanation of symbols]

[0143] 0 Electrochemical Cell 1. First Section 2 Second Section 3 membrane 4 anodes 5 cathode 6 First Electrical Lead 7. Voltage Source 8 Second Electrical Lead 9 Unassigned 10 Supplies 11 Unassigned 12 Poor working medium 13 Wealth Working Media 14 Wastewater 15 Target product 16 Separation device H2O Water H2 Hydrogen O2 oxygen LiOH Lithium hydroxide OH - OH anion Li + Lithium-cation U Voltage I current A active area C F LiOH concentration in the feed C W LiOH concentration in wastewater C M0 LiOH concentration in the poor working medium C M1 LiOH concentration in the working medium

Claims

1. A process for producing hydrogen and lithium hydroxide, a) A step of providing a feed comprising at least water, Li ions, and impurities, wherein the concentration of Li ions in the feed is C Ｆ The step of providing a supply, wherein in each case the supply is at least 200 ppm (by weight) or between 500 ppm (by weight) and 140,000 ppm (by weight), based on the total weight of the supply; b) A step of providing a poor working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration of lithium hydroxide in the poor working medium is C Ｍ０ The step of providing a poor working medium, which is at least 50 ppm (by weight) based on the total weight of the poor working medium; c) The step of providing at least one electrochemical cell, the electrochemical cell having the following characteristics: i. The electrochemical cell includes a first compartment in which an anode is located; ii. The electrochemical cell includes a second compartment in which a cathode is located; iii. The electrochemical cell includes a membrane that separates the first membrane from the second membrane and has an area A; iv. The film comprises an inorganic material that is conductive to Li ions and electrically insulating; d) Providing at least one voltage source connected to the anode via a first electrical lead and to the cathode via a second electrical lead; e) The step of filling the first compartment with the supply; f) The step of filling the second compartment with the poor working medium; g) A step of charging the electrochemical cell with a voltage U drawn from the voltage source such that a current I flows between the anode and the cathode, wherein the ratio Q of the current intensity of the current I to the area A of the film is 100 A / m ２ ~500 A / m ２ During or at 150 A / m ２ ~350 A / m ２ The charging step is during this period; h) A step of drawing wastewater from the first compartment, which contains at least water, Li salts dissolved therein, oxygen, and impurities, wherein the concentration of Li ions in the wastewater is C Ｗ However, based on the total weight of the wastewater, the concentration of Li ions in the feed based on the total weight of the feed is C Ｆ A lower step in the extraction process; i) A step of withdrawing a rich working medium containing water, hydrogen, and lithium hydroxide from the second compartment, wherein the concentration C of lithium hydroxide in the rich working medium based on the total weight of the rich working medium Ｍ１ is higher than the concentration C of lithium hydroxide in the lean working medium based on the total weight of the lean working medium Ｍ０ and the concentration C of lithium hydroxide in the rich working medium based on the total weight of the rich working medium Ｍ１ is higher than the solubility of lithium hydroxide in water at a temperature T Ｍ１ wherein the temperature T Ｍ１ refers to the temperature of the rich working medium when withdrawn from the second compartment, the withdrawing step, a process including.

2. The process according to claim 1, characterized in that the rich working medium contains solid lithium hydroxide when drawn from the second compartment.

3. The temperature T of the working medium when it is drawn out from the second compartment. Ｍ１ The process according to claim 1, characterized in that the temperature is between 20°C and 60°C.

4. The concentration C of lithium hydroxide in the enriched working medium based on the total weight of the enriched working medium. Ｍ１ However, if the amount is greater than 0.1276 kg / kg, or greater than 0.138 kg / kg, or greater than 0.146 kg / kg, it is calculated as LiOH in each case; or The concentration C of lithium hydroxide in the enriched working medium based on the total weight of the enriched working medium. Ｍ１ However, it is greater than 0.21 kg / kg or greater than 0.231 kg / kg, and in each case LiOH·H ２ It is calculated as O. The process according to claim 3.

5. The concentration C of lithium hydroxide in the poor working medium based on the total weight of the poor working medium. Ｍ０ The process according to claim 1, characterized in that the amount is less than 12.8% (by weight).

6. The process according to claim 1, characterized in that the feed contains an anion selected from the group consisting of sulfates, carbonates, hydroxides, and chlorides.

7. The process according to claim 1, characterized in that the feed contains impurities in the form of compounds of elements selected from the group consisting of B, Na, Mg, Al, Si, K, Ca, Mn, Fe, Co, Ni, Cu, and C.

8. The inorganic material present in the aforementioned film was measured by the "impedance spectroscopy" method described herein, and at a temperature of 23°C, it was found to be at least 1 * 10 －５ S / m or at least 5*10 －５ S / m or at least 10*10 －５ S / m and 100*10 －５ The process according to claim 1, having Li ion conductivity of S / m or less.

9. The inorganic material is a compound of the following stoichiometric type (LATP): 【Chemistry 1】 [In the equation, 0.1 ≤ x ≤ 0.3] The process according to claim 8, characterized in that it is the process described above.

10. The inorganic material is a compound with the following stoichiometric properties (LATSP): 【Chemistry 2】 [In the equation, 0.1 ≤ x ≤ 0.3 and 0.2 ≤ y ≤ 0.4] The process according to claim 8, characterized in that it is the process described above.

11. The inorganic material is a compound of the following stoichiometric type (LAGTSP): 【Transformation 3】 [In the equation, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, and 0 ≤ n ≤ 1.] The process according to claim 8, characterized in that it is the process described above.

12. The inorganic material is a compound of the following stoichiometric type (LAGTP): 【Transformation 5】 [In the equation, 0 ≤ x ≤ 1] The process according to claim 8, characterized in that it is the process described above.

13. The inorganic material is a compound (LAGP) of the following stoichiometry: 【Chemistry 4】 [where x = 0 or x = 0.2 or x = 0.4] The process according to claim 8, characterized in that it is as such.

14. The inorganic material is a compound (LLTO) of the following stoichiometry: 【Transformation 6】 [where 0 ≤ x ≤ 0.16] The process according to claim 8, characterized in that it is as such.

15. The following additional steps: k) Providing a separation device; l) Separating the lithium hydroxide from the rich working medium using the separation device, The process according to claim 1, comprising the above.

16. The process according to claim 15, wherein l) In the step of separating the lithium hydroxide from the rich working medium using the separation device, The following composition: Lithium hydroxide: > 56.5% (by weight) Water: < 43.5% (by weight) Carbon dioxide: < 0.35% (by weight) Sulfur dioxide: < 0.01% (by weight) Chlorine: < 0.002% (by weight) Calcium: < 15 ppm (by weight) Iron: < 5 ppm (by weight) Sodium: < 20 ppm (by weight) Aluminum: < 10 ppm (by weight) Chromium: < 5 ppm (by weight) Potassium: < 10 ppm (by weight) Copper: < 5 ppm (by weight) Nickel: < 10 ppm (by weight) Silicon: < 30 ppm (by weight) Zinc: < 10 ppm (by weight) Other substances: < 10% (by weight) [The parts by weight total 100% and are based on the total weight of the product] The process by which a product having the above is obtained.

17. l) The step of separating the lithium hydroxide from the rich working medium using the separation device Results in the lean working medium, whereby b) A step of providing a poor working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration of lithium hydroxide in the poor working medium is C Ｍ０ However, the step of providing a poor working medium that is at least 50 ppm (by weight) based on the total weight of the poor working medium is Performed using the separation device, The process according to claim 15.

18. The process according to claim 15, characterized in that the electrochemical cell and the separation device are provided at the same location.

19. At least the process steps i) Withdrawing a rich working medium containing water, hydrogen and lithium hydroxide from the second compartment; And l) Separating the lithium hydroxide from the rich working medium using the separation device; The process according to claim 18, characterized in that they are performed continuously.

20. The process according to claim 15, characterized in that the separation device is a solid separator.

21. The process according to claim 20, characterized in that the separation device is selected from the group consisting of the following solid separators: filters, hydrocyclones, and sedimentation separators.

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