Production of hydrogen and solid lithium hydroxide

Abstract

The problem addressed by the present invention is that of specifying a process for producing lithium hydroxide which is very energy efficient. The process shall especially operate without consumption of thermal energy. The process shall be able to handle, as raw material, Li-containing waters generated during digestion of spent lithium-ion batteries. The LiOH produced by the process shall have a high purity sufficient for direct manufacture of new LIB. The process shall achieve a high throughput and have small footprint in order that it can be combined with existing processes for workup of used LIB / for production of new LIB to form a closed, continuous production loop. The process according to the invention is an electrolytic membrane process operating with a LiSICon membrane. It is a special aspect of the process that the electrolysis is operated up to the precipitation limit of the lithium hydroxide.

Description

[0001] Production of hydrogen and solid lithium hydroxide

[0002] Lithium (Li) is essential for the production of lithium-ion batteries (LIEB). Due to its high reactivity, lithium does not occur naturally as a pure substance, but always in a bound form. The starting material for the production of LIEB is usually lithium hydroxide (LiOH) or lithium carbonate (Li2CO3).

[0003] In most natural deposits, Li is present in the form of lithium oxide (Li2O) or salts such as lithium sulfate (U2SO4) or lithium chloride (LiCl). Lithium oxide is a component of ores such as pegmatite, while lithium sulfate and lithium chloride are dissolved in the lye of Li salt lakes. During mining, the extracted lithium compound is converted into lithium carbonate (U2CO3). In a further process step, the lithium carbonate can be converted into lithium hydroxide using quicklime or calcium hydroxide. The extraction of Li and its conversion to LiOH is described in:

[0004] 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

[0005] Rich lithium deposits are known, but the production of LiOH from the lithium compounds found there is highly energy- and wastewater-intensive. Furthermore, there is a strategic need to be independent of the deposit owners.

[0006] One solution to this problem could be to recycle used LIBs so that the lithium they contain can be reused as a raw material for new batteries.

[0007] Recycling processes for LIBs have already been developed to technical maturity in the past, but mostly with the goal of recovering the metals they contain, such as Fe, Ni, Mn, Co, Mg, and Al. The alkali metal Li was generally not recovered because its high reactivity makes it difficult to separate from battery scrap, and it was available in sufficient quantities and inexpensively from natural deposits. For a long time, the extraction of Li from used LIBs simply seemed uneconomical.

[0008] Meanwhile, social and economic pressure to recover lithium from used LIBs has increased. The success of this project requires that recycled lithium can be offered in a quality acceptable to LIB producers, so that the manufacturing processes for LIB from recycled lithium do not differ from those for mined fresh lithium. Battery quality must, of course, not suffer. Consequently, recycled lithium, especially in the form of LiOH, must meet very demanding purity specifications. Furthermore, the process for recovering lithium from used batteries must be as energy-efficient as possible. The process should also consume little water. Known processes for recovering lithium from used batteries have been compiled:

[0009] 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.

[0010] A technology that is only mentioned in passing as “LISM” in the above review article is the electrolysis of Li-containing waters in the presence of so-called LiSICon membranes.

[0011] LiSICon stands for Lithium Super Ionic Conductor. It is a class of inorganic, (glass) ceramic material that is electrically insulated but also has intrinsic conductivity for lithium ions. The transport mechanism for lithium is based on the material's crystal structure. Simply put, the lithium ions are "passed through" the crystals. 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-state electrolytes for LIBs. An overview of LiSICon's transport mechanisms, their crystal structure, and production can be found at:

[0012] 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

[0013] 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 / acsener- gylett.7b00849

[0014] Spezielle LiSICon Stöchiometrien werden beschrieben von:

[0015] Sofia Saffirio et al.Lii 4Alo 4Geo4Tii 4(P04)3 promising 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 .1 1 .014.

[0016] Eongyu Yi et al. Materials that can replace liquid electrolytes in Li batteries: Superionic conductivities in Li1 7AI03Ti1 7Si04P26O12. 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. Due to their selective conductivity for Li ions, LiSICon materials can be used as membranes to separate Li from Li-containing mixtures. The Li must be present in the mixture in ionic form, for example, as a Li salt dissolved in water. An electrical voltage is required as the driving force to transport the Li ions through the LiSICon membrane. For this purpose, an electrochemical cell is constructed, comprising two electrodes and a LiSiCon membrane that divides the cell into two compartments. Each compartment contains an electrode.Depending on the polarity of the electrode contained in the compartment, the compartments are referred to as anodic or cathodic. An electrical voltage is applied to the electrodes, and the Li-containing water, known as the anolyte, is poured into the anionic compartment. The cathodic compartment is filled with water, known as the catholyte. The membrane passes the Li cations to the cathode. The water in the cathodic compartment (catholyte) is therefore enriched in Li, while the water on the anodic side (anolyte) is depleted of Li. Such a process is called membrane electrolysis.

[0017] Membrane electrolytic processes for the extraction of lithium using LiSICon membranes have already been described in the state of the art.

[0018] Zhen Li et al. describe a process that uses the low-lithium water of the Red Sea as a raw material:

[0019] Zhen Li et al.: Continuous electrical pumping membrane process for seawater lithium mining. Energy Environment. Sci., 2021 , 14, 3152 DOI: 10.1039 / d1 ee00354b

[0020] Zhen Li's research group uses LLTO as a membrane. The separated target product is lithium phosphate (OI3PO4), which is a potential candidate for the production of lithium iron phosphate (LFP) batteries. LIBs with a different cathode material, such as nickel manganese cobalt (NMC) or lithium manganese oxide (NMO), cannot be directly produced with this method.

[0021] Using solar power, a LAGP membrane, and a copper foil, Yang et al. aim to extract metallic lithium directly from seawater:

[0022] 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.

[0023] US 2016 / 0201163 A1 describes the separation of Li ions from a brine such as seawater using LiSiCon membranes. The membrane materials used are LisN, LiwGeP2Si2, and La x Li y TiO2, Lii+ x + y Al x (Ti, Ge)2- x Si y P3- y Oi2 is proposed. The target product is lithium carbonate (U2CO3).

[0024] WO 2019055730 A1 also deals with the separation of lithium using LiSICon membranes. Specifically, LLTO, LAGP, or LATP are mentioned. The LiSICon material can be applied to a support structure. The chemical nature of the support structure is not described in detail. Nor is it described how LiSICon is applied to the support structure. The separated target product is lithium ions.

[0025] From US9222148B2, it is known to separate lithium hydroxide by electrolysis on a LiSICon membrane and then precipitate lithium hydroxide hydrate. The disadvantage of this process is that it requires an energy-intensive evaporation step to precipitate the lithium hydroxide.

[0026] US 20120103826 A1 describes the electrodialytic separation of lithium hydroxide from contaminated streams using a LiSICon membrane. To achieve high purity, LiOH is precipitated from the brine. This takes advantage of the fact that LiOH has a lower solubility in water than the foreign salts. The precipitate is then redissolved and fed into the electrodialysis cell. The concentration of LiOH in the catholyte of the electrodialysis cell is not specified in US 20120103826 A1. The catholyte is diluted with water. The disadvantage of this process is that a complex crystallization process must be carried out prior to electrolysis, and the heat of crystallization is lost through the redissolution of the precipitate. The process is therefore technically complex and energy-intensive.

[0027] In addition to the use of ceramic LiSICon membranes, electrolytic processes for the separation of lithium are also known, which work with organic ion exchange membranes.

[0028] EP 3805428 A1 describes the electrolytic production of lithium hydroxide. In addition to electrolysis, an electrochemical conversion of lithium to lithium hydroxide is carried out. To obtain the necessary reactants, water is simultaneously split electrochemically. A bipolar three-chamber cell with an ion exchange membrane is used for this purpose. The commercial ion exchange membranes used are Asahi® AW, Nation® 902, Fumatech® FAB, Fumatech® FKB, and Neosepta® CMB. The chemical nature of these ion exchange membranes is not disclosed in EP 3805428 A1, but it is highly likely that they are organic membrane materials. The three-chamber cell operates in an acidic environment. Water containing lithium salts, such as lithium sulfate (U2SO4) or lithium chloride (LiCl), is used as feed.

[0029] A two-stage electrodialytic / electrolytic production of lithium hydroxide from aqueous lithium sulfate and / or lithium bisulfate with simultaneous water splitting is disclosed in US 10036094 B2. A two-compartment electrochemical cell is used in the first stage, and a three-compartment cell is used in the second stage. The cells are equipped with ion exchange membranes. The chemical composition of the membranes is not disclosed. The following commercial membranes are mentioned: Fumatech® FAB, Astom® ACM, Asahi® MV, Nation® 324, or Astom® AHA. A fundamental disadvantage of polymer membranes is their water permeability. This dilutes the anolyte with water from the catholyte. This requires subsequent dewatering of the target product, which in turn consumes thermal energy or limits the plant location to sunny regions.

[0030] In addition to their water permeability, a fundamental disadvantage of organic ion exchange membranes is that they are less ion-selective than inorganic LiSICon materials: They not only allow Li + , but also Na + happen, so that the purity of the target product is impaired as soon as sodium is present in the feed. In addition to the purity of the target product, the power efficiency of the process also suffers: The valuable electrical energy is also used in electrolysis with non-ion-selective membranes to remove unwanted Na + into the second compartment. Once in the second compartment, the Na + Furthermore, it is converted into unwanted byproducts via unintended electrochemical processes. The energy efficiency of the process is limited in relation to the yield of the target product Li.

[0031] Finally, organic membranes are sensitive to the presence of divalent cations such as Mg 2+ and Ca 2+ These cations poison the membrane over time, limiting the service life of organic ion exchange membranes.

[0032] The (glass)ceramic LiSICon materials promise better ion selectivity. However, a highly relevant problem for industrial practice continues to be the stability of the LiSICon membrane towards impurities. For example, the Li + -containing waters that arise during the processing of used LIB, other cations such as Na + and K + , which cause lasting damage to the LiSICon material: These cations apparently permanently occupy the defects in the crystal structure, so that transport of the Li +-cations through the membrane is hardly possible any more. The service life of the electrochemical cell is then over. Because LiSICon material is very expensive, recycling Li from LIB is uneconomical given the short lifetime of the membrane. The brine from Li-salt lakes also naturally contains high levels of sodium and therefore cannot be released onto known LiSICon membranes. Therefore, lithium from salt lakes continues to be thermally separated, an energy-intensive process, and / or is gradually dissolved and recrystallized using large amounts of water. Although the water is evaporated by solar radiation, the water needed to dissolve LiCl is scarce in the deserts of South America. This method therefore leads to major problems there.

[0033] Another practical problem is the high specific electrical resistance of the LiSiCon material. This results in a high internal resistance of the electrochemical cell, resulting in a correspondingly high electrical energy requirement for the process. To reduce this, the membrane could theoretically be thinned. However, due to its thin material, its service life in aggressive environments would then be limited.

[0034] In view of this prior art, the object of the invention is to provide a process for the production of lithium hydroxide that is highly energy-efficient. In particular, the process should operate without the consumption of thermal energy. As a raw material, the process should be able to process Li-containing water that arises during the disintegration of used lithium-ion batteries. The LiOH produced by the process should have such a high purity that it can be used directly for the production of new LIBs. The process should achieve high throughput and have a low space requirement so that it can be combined with existing processes for the processing of used LIBs or for the production of new LIBs to form a closed, continuous production cycle. Finally, the process should require as little fresh water as possible and generate little wastewater.

[0035] This object is achieved by a method according to claim 1 .

[0036] The invention therefore relates to a process for producing hydrogen and lithium hydroxide, comprising the following steps: a) providing a feed containing at least water, Li ions, and impurities, wherein the concentration of Li ions in the feed CF 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 containing water and lithium hydroxide dissolved therein, wherein the concentration of lithium hydroxide in the lean working medium CMO is at least 50 ppm by weight, based on the total weight of the lean working medium; c) providing at least one electrochemical cell, wherein the electrochemical cell has the following features: i) the electrochemical cell comprises a first compartment in which an anode is arranged; ii) the electrochemical cell comprises a second compartment in which a cathode is arranged;iii) the electrochemical cell comprises a membrane which separates the first compartment from the second compartment, the membrane having an area A; iv) the membrane contains an inorganic material which is conductive for Li ions and which is electrically insulating; d) providing at least one electrical voltage source which is connected to the anode via a first electrical line and to the cathode via a second electrical line; e) supplying the first compartment with the feed; f) supplying the second compartment with the lean working medium; g) supplying the electrochemical cell with an electrical voltage U obtained from the electrical voltage source, such that an electrical current / flows between the anode and the cathode, the quotient Q of the current intensity of the electrical current / and the area A of the membrane being between 100 A / m; 2 and 500 A / m 2or between 150 A / m 2 and 350 A / m 2h) withdrawing wastewater containing at least water, Li salts dissolved therein, oxygen, and impurities from the first compartment, wherein the concentration of Li ions in the wastewater Cw based on the total weight of the wastewater is lower than the concentration of Li ions in the feed CF based on the total weight of the feed;i) withdrawing a rich working medium containing water, hydrogen and lithium hydroxide from the second compartment, wherein the concentration of lithium hydroxide in the rich working medium CMI based on the total weight of the rich working medium is greater than the concentration of lithium hydroxide in the lean working medium CMO based on the total weight of the lean working medium and wherein the concentration of lithium hydroxide in the rich working medium CMI based on the total weight of the rich working medium is greater than the solubility of lithium hydroxide in water at a temperature 7MI, wherein the temperature 7MI denotes the temperature of the rich working medium at the time of its withdrawal from the second compartment;

[0037] The process according to the invention is an electrolytic membrane process which works with a LiSICon membrane.

[0038] An important aspect of the process according to the invention is that the lithium is selectively separated by the membrane and water electrolysis occurs simultaneously in the cell. During water electrolysis, water (H2O) is electrochemically separated into H2 and O2. OH- and hydrogen are formed at the cathode. However, the OH- anions cannot overcome the LiSiCon membrane and combine with the Li arriving in the cathodic compartment. + -cations to lithium hydroxide LiOH. At the anode, oxygen and H + formed.

[0039] When Li+ membrane separation and water electrolysis are operated simultaneously in an electrochemical cell with a LiSICon membrane, lithium hydroxide (LiOH) and molecular hydrogen (H2) are directly produced. Both are dissolved in water. The water, along with the LiOH and H2, is extracted from the cathodic compartment of the cell. The LiOH is separated from the water. This produces LiOH that has the appropriate purity due to the selective lithium ion migration through the membrane and can be used in battery production.

[0040] The hydrogen produced at the same time can be captured and used in the hydrogen economy. If the electrochemical cell is powered by green electricity, the process also leaves a low carbon footprint.

[0041] As feed for the combined Li separation and water electrolysis, a water containing Li +Cations are required. Such water is either generated during the processing of spent LiB or a Li brine from a natural deposit is used.

[0042] A key aspect of the process is that the electrolysis is carried out up to and beyond the precipitation limit of lithium hydroxide. Consequently, the concentration of lithium hydroxide in the rich working medium (CMI) relative to the total weight of the rich working medium is greater than the solubility of lithium hydroxide in water. The lithium hydroxide can thus precipitate as a solid in the catholyte, provided the necessary crystallization nuclei are present. Since these are always present in the form of minor impurities, the LiOH precipitates at least partially as a solid in the rich working medium (catholyte).

[0043] The point at which the lithium hydroxide precipitates as a solid in the catholyte depends on the cell's operating conditions and the presence of crystallization nuclei: The lithium hydroxide can precipitate as a solid in the second compartment or only immediately after the rich working medium is withdrawn, i.e., only outside the cell. In either case, the rich working medium withdrawn from the second compartment contains solid lithium hydroxide according to the invention.

[0044] Preferably, the rich working medium contains lithium hydroxide as a solid at the time of its withdrawal from the second compartment.

[0045] Solid lithium hydroxide ideally means lithium hydroxide in crystalline form. Since lithium hydroxide crystals can retain water, lithium hydroxide can also exist as a gel. In the gel, the lithium hydroxide forms a solid phase, while the water forms a liquid phase. Gel formation is also determined by the remaining impurities in the second compartment. This means that, depending on the thermodynamic conditions in the second compartment and the concentration of lithium hydroxide and impurities there, the lithium hydroxide precipitates as a gel. A gel containing solid lithium hydroxide and liquid water is therefore also considered a solid within the meaning of the invention. The term "solid" therefore encompasses both a crystalline form and a gel.The precipitation limit of lithium hydroxide in the second compartment is reached when the concentration of lithium hydroxide in the rich working medium CMI based on the total weight of the rich working medium is greater than the solubility of lithium hydroxide in water at a temperature 7MI , where the temperature 7MI is the temperature of the rich working medium at the time of its withdrawal from the second compartment.

[0046] The solubility of lithium hydroxide in water is temperature-dependent, as is the case with most water-soluble inorganic solids. The exact position of the precipitation limit thus depends on the temperature of the rich working medium. According to the invention, the temperature TMI is used, at which the rich working medium is withdrawn from the second compartment. The temperature 7MI is ideally between 20°C and 60°C. In the simplest case, this temperature corresponds to the operating temperature of the electrochemical cell. However, it is also conceivable to operate the cell at a higher temperature and cool the rich working medium to TMI immediately before or during withdrawal. However, this is not always energetically feasible.

[0047] In practice, the solubility of lithium hydroxide in water also depends on the purity of the water. If the water contains impurities, these act as crystallization nuclei and promote the precipitation of lithium hydroxide.

[0048] Finally, it makes a difference whether the concentration of lithium hydroxide is calculated in the form of its anhydride (LiOH) or in the form of its monohydrate (LiOH^F ).

[0049] All this apparently leads to the fact that the solubility of lithium hydroxide is not consistently stated in scientific literature or in patent applications.

[0050] Monnin and Dubois have presented a comprehensive review of the solubility of lithium hydroxide in water:

[0051] Christophe Monnin and Michel Dubois: Thermodynamics of the LiOH + H2O System. Chem. Eng. Data 2005, 50, 4, 1 109-1113 DOI 10.1021 / je0495482

[0052] In addition, Monnin and Dubois mathematically interpolated the values ​​known from the literature.

[0053] The solubility of lithium hydroxide in water at relevant temperatures according to different authors is shown in Table 1: Table 1 : Solubility of LiOH in water

[0054] * Values ​​according to Ullmann and KirkOthmer calculated as monohydrate, other values ​​calculated as anhydride

[0055] The values ​​presented in Table 1 are taken from the following literature sources

[0056] Dittmar: DOI https: / / doi.Org / 10.1016 / 0016-0032(89)90312-8

[0057] D1 : US 2012103826 A1

[0058] S&M: DOI https: / / doi.org / 10.1021 / je60015a018

[0059] Xie et al: DOI https: / / doi.Org / 10.1016 / j.seppur.2023.123972

[0060] M&D: DOI https: / / doi.org / 10.1021 / je0495482

[0061] KirkOthmer: DOI https: / / d0i.0rg / l 0.1002 / 0471238961 .1209200811011309. a01 ,pub2

[0062] Ullmann: DOI https: / / doi.org / 10.1002 / 14356007.a15_393.pub2

[0063] Given the desired temperature range 7MI of 20°C to 60°C, the concentration of lithium hydroxide in the rich working medium CMI, based on the total weight of the rich working medium, is preferably above 0.1276 kg / kg (according to Table 1, this is the lowest reported solubility of LiOH in water at a temperature of 333.15 K = 60°C). Preferably, the concentration of lithium hydroxide in the rich working medium CMI, based on the total weight of the rich working medium, is above 0.138 kg / kg or above 0.146 kg / kg. These values ​​are calculated as LiOH anhydride. If the concentration is determined as lithium hydroxide monohydrate, the concentration of lithium hydroxide in the rich working medium CMI should be above 0.23 kg / kg or above 0.256 kg / kg.

[0064] The concentration of lithium hydroxide in the lean working medium (CMO) should be less than 12.8 wt.% relative to the total weight of the lean working medium. This ensures that the LiOH is not introduced into the second compartment as a solid. The lower limit for the LiOH concentration in the lean working medium is 50 ppm. Otherwise, the reaction will not start or proceed.

[0065] In connection with the representation of the solubility of lithium hydroxide in water, it should be made clear that the cell does not have to be operated exactly at the solubility limit. The cell is intended to be operated above the precipitation limit so that a particularly high amount of LiOH precipitates as a solid. The upper limit for CMI is determined by the pumpability of the rich working medium: If this contains too much solid lithium hydroxide, it can no longer be pumped out of the second compartment. The LiOH concentrations given in Table 1 therefore correspond to the lower limit for CMI. The upper limit results from the apparatus design of the plant used to carry out the process according to the invention. In particular, the design of the conveying equipment, which carries out the extraction of the rich working medium from the second compartment and its transport to a downstream separation device, is decisive for the upper limit.The separation apparatus is used in the implementation of the inventive process to separate LiOH from the rich working medium. In addition to the conveying equipment, bottlenecks in the cell and pipe connections can also become clogged by crystallizing product, thus also defining the technically manageable upper limit for CMI.

[0066] Since the inorganic membrane is insensitive to foreign ions, the feed can contain anions selected from the group consisting of sulfate, carbonate, hydroxide, chloride.

[0067] 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 byproducts of lithium from natural deposits, while the other metals mentioned are used as conductor or cathode materials in LIBs and are therefore found in feeds obtained from the reprocessing of used LIBs. Carbon is also found in valuable material streams from the reprocessing of used LIBs and originates from polymeric components of battery cells, such as films, separators, adhesives, or sealants.

[0068] According to the invention, a membrane containing an inorganic material is used. Unlike polymer membranes, this allows the required ion selectivity to be achieved. Preferably, the membrane consists entirely of the inorganic material. Composite membranes that contain the inorganic material only as a coating on a support material or in which the inorganic material is dispersed in a different matrix material have proven to be a mistake.

[0069] For the process to work, the inorganic material must conduct Li ions while simultaneously insulating them electrically. The specific conductivity for electrons g (electrical conductivity) should be less than 10 at a temperature of 23°C. -7 S / cm (10 -9 S / m) or less than 10 -12 S / m or less than 10' 18S / m. Therefore, the inorganic material is classified as a non-conductor from an electron-conducting perspective. The specific conductivity s of the inorganic material for Li-ions should 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 maximum 100*10 -5 S / m. The Li conductivity of the material is measured using impedance spectroscopy. This measurement is performed as follows:

[0070] The measurement setup consists of two cylindrical electrodes between which the sample is placed. To ensure optimal contact with the electrodes and reproducible contract pressure, a weight is placed on the sample.

[0071] A potentiostat (ZAHNER-elektrik I. Zahner-Schiller GmbH & Co. KG, Kronach-Gundelsdorf, Germany) is connected to the electrodes and controlled by Thales software (ZAHNER). Measurements are performed in a frequency range of 1 Hz to 4 MHz and an amplitude of 5 mV using polished samples onto which a thin, conductive gold layer has been sputtered.

[0072] The measurement results are presented in Nyquist diagrams and evaluated using the Analysis software (ZAHNER). The electrical resistance is read from the maximum of the Nyquist diagram curve. The specific ionic conductivity o [mS / cm] is then calculated using the formula a=(h-10 4 ) / (R-TT / 4-d 2 ), where h is the height of the sample in mm, R is the measured electrical resistance in Q and d is the diameter of the sample in mm.

[0073] LiSICon is preferably used as the inorganic material. LiSICon materials are (glass) ceramic materials that conduct lithium ions while simultaneously electrically insulating them. In principle, all known LiSICon materials can be used as inorganic materials within the meaning of the invention. Known LiSICon materials meet the above-mentioned requirements for both the electrical conductivity and the ionic conductivity of the inorganic material.

[0074] For example, the LiSICon material lithium aluminum titanium phosphate (LATP) can be used. Accordingly, a variant of the invention provides that the inorganic material is a compound with the following stoichiometry:

[0075] Lii+xAlxTi2-x(PO4)3 where: 0.1 <x<0.3, wobei bevorzugt gilt x=0.3.

[0076] Alternatively, the LiSICon material lithium aluminum titanium silicon phosphate (LATSP) can be used. Accordingly, a variant of the invention provides that the inorganic material is a compound with the following stoichiometry: LiI+x+yAlXTi2-xSiYP3-yOl2, where: 0.1 <x<0.3 und 0.2<y<0

[0077] A particularly preferred embodiment of the invention provides for the use of a LAGTSP that additionally contains germanium. A LAGTSP is available, for example, from OHARA GmbH, Hofheim, Germany, under the product name LICGC® AG01.

[0078] The stoichiometry of LAGTSP is:

[0079] Lii+x+yAlxTi2-xSiyP3-yOi2 * nGeO2 where: 0 <x<1 und 0<y<1 und 0<n<1.

[0080] Alternatively, the LiSICon material lithium aluminum germanium phosphate (LAGP) can be used. Accordingly, a variant of the invention provides that the inorganic material is a compound with the following stoichiometry:

[0081] Lii+xAlxGe2-x (PÜ4)3 where: x=0 or x=0.2 or x=0.4.

[0082] However, a LiSICon derived from lithium aluminum germanium phosphate (LAGP) but also containing titanium is particularly preferred. It is referred to as LAGTP.

[0083] Accordingly, a preferred variant of the invention provides that the inorganic material is a compound of the following stoichiometry:

[0084] Lii 4Alo 4(Gei-xTix)i 6 (PÜ4)3 where: 0 <x<1 .

[0085] As an alternative to the aforementioned phosphates, the oxide LiSICon material lithium lanthanum titanium oxide (LLTO) can be used. Accordingly, a variant of the invention provides that the inorganic material is a compound with the following stoichiometry:

[0086] Li3xLa ( 2 / 3)-xn ( 1 / 3)-2xTiO3 where: 0 <x<0.16.

[0087] The lithium hydroxide is contained in the rich working medium and is withdrawn from the second compartment with it. To make it usable, it must be separated from the rich working medium. A separation apparatus is provided for this purpose. A preferred development of the invention therefore provides the following additional process steps: k) Providing a separation apparatus; l) Separating lithium hydroxide from the rich working medium using the separation apparatus.

[0088] Preferably, the process is carried out in such a way that a product is separated with the aid of the separation apparatus which has the following composition:

[0089] Lithium hydroxide: >56.5 wt%

[0090] Water: <43.5 wt%

[0091] Carbon dioxide: <0.35 wt%

[0092] Sulphur dioxide: <0.01 wt%

[0093] Chlorine: <0.002 wt%

[0094] Calcium: <15 ppm by weight

[0095] Iron: <5 ppm by weight

[0096] Sodium: <20 ppm by weight

[0097] Aluminum: <10 ppm by weight

[0098] Chromium: <5 ppm by weight

[0099] Potassium: <10 ppm by weight

[0100] Copper: <5 ppm by weight

[0101] Nickel: <10 ppm by weight

[0102] Silicon: <30 ppm by weight

[0103] Zinc: <10 ppm by weight

[0104] Other substances: <10 wt%, whereby the weight fractions add up to 100% and are based on the total weight of the product. One such product is "battery-grade" LiOH and can be used directly in the production of LIBs.

[0105] The product separated in the separation apparatus contains solid lithium hydroxide. The product preferably meets the above specification so that it can be used directly as "battery-grade LiOH" for the production of new LIBs. However, the separated product is not pure LiOH; inherently, the separated product will always contain water enclosed in the LiOH crystals (water of crystallization / internal water). However, the water content of the separated product is below 43.5 wt.% and therefore meets the "battery-grade" specification. At this water content, the separated product is a crystalline solid and not a gel. The working fluid, which was freed of LiOH in the separation apparatus, is pumped back into the electrochemical cell as a lean working fluid and recharged there. The working fluid is thus conducted in a closed circuit.The working fluid circuit is created between the second compartment and the separation device. This working fluid circuit eliminates both the need for fresh water and wastewater disposal.

[0106] It is important that the lean working medium is not completely free of LiOH, but rather has a certain minimum CMO concentration of approximately 50 ppm by weight. Otherwise, the process in the cell could not be maintained continuously. Therefore, the separation device does not completely separate the LiOH contained in the rich working medium, but leaves a residual concentration in the working medium. Preferably, the separation device separates only solid LiOH and leaves dissolved LiOH in the working medium as the initial CMO concentration.

[0107] A preferred development of the invention therefore provides the following additional process steps:

[0108] I) separating lithium hydroxide from the rich working medium with the aid of the separation apparatus so that the lean working medium is obtained, wherein step b) providing a lean working medium containing water and lithium hydroxide dissolved therein, wherein the concentration of lithium hydroxide in the lean working medium CMO is at least 50 ppm by weight based on the total weight of the lean working medium; is carried out with the aid of the separation apparatus.

[0109] To enable the circulation of the working medium between the separation device and the second compartment, it makes sense to locate both devices at the same location. This same location is considered to be a continuous production facility. Consequently, the electrochemical cell and separation device are part of a continuous facility. Thanks to the closed working medium circuit, the electrochemical cell and separation device can be located at the same location and operated continuously. Preferably, the process is directly integrated into a network that includes a facility for reprocessing used LIBs and a facility for producing new LIBs. However, it is also possible to combine the process with a battery recycling facility and export the recovered LiOH. It is also conceivable to locate the separation device at a different location away from the electrochemical cell.However, the working fluid would then have to be transported between the cell and the separation device. This hardly makes sense from an energy perspective.

[0110] Preferably, at least the electrochemical cell is operated continuously. This means that both compartments are continuously flowing. The feed flows through the first compartment, producing wastewater, while the working medium flows through the second compartment, flowing in as a lean working medium and flowing out as a rich working medium. This allows for a higher throughput, while also continuously removing membrane-damaging components in the feed and working medium. Therefore, better membrane durability can be expected in continuous operation than in batch operation.

[0111] A preferred embodiment of the process therefore provides that at least the process steps i) withdrawing a rich working medium containing water, hydrogen and lithium hydroxide from the second compartment; and

[0112] I) Separation of lithium hydroxide from the rich working medium using the separation apparatus; this should be done continuously.

[0113] Since the LiOH is produced as a solid in the process according to the invention, the separation apparatus is preferably designed as a solid-state separator. Suitable solid-state separators are filters, hydrocyclones, and settling tanks. These apparatuses operate without thermal energy. Consequently, the process described here primarily requires electrical energy to operate the electrochemical cell and secondary electrical energy to convey the material streams. The process can therefore preferably be operated with green electricity. Figure description:

[0114] The invention will now be explained in more detail using process flow diagrams. These are shown in:

[0115] Figure 1 : Functional principle of simultaneous membrane electrolysis of Li + and water electrolysis in electrochemical cell with LiSICon membrane;

[0116] Figure 2: Functional principle of the circuit between the electrochemical cell and the separation device.

[0117] 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. Both compartments 1, 2 are separated from each other by a membrane 3. An anode 4 is arranged in the first compartment 1. A cathode 5 is arranged in the second compartment 2. The first compartment 1 can therefore also be referred to as the anodic compartment, while the second compartment 2 is referred to as the cathodic compartment.

[0118] A first electrical line 6 connects the anode 4 to a voltage source 7. A second electrical line 8 connects the cathode 5 to the voltage source 7. The polarity of the voltage source 7 is selected such that the positive pole of the voltage source 7 is connected to the anode 4, while the negative pole of the voltage source 7 is connected to the cathode 5.

[0119] An electric current / flows through the two electrical lines 6, 8 and via the electrical voltage source 7. Since the membrane 3 is electrically insulated, there is no electrical short circuit between the two electrodes 4, 5 via the membrane 3.

[0120] Membrane 3 is a flat membrane made entirely of LiSiCon material. Anode 4 is a flat metallic sheet containing titanium, niobium, or tantalum. Cathode 5 is also a flat metallic sheet containing titanium or nickel. In the simplest case, stainless steel sheet is used as the cathode. Anode 4, cathode 5, and membrane 3 have the same shape; they can be rectangular or circular. This is not visible in the side view of Figure 1. Instead of sheets, expanded metal, grids, or meshes made of the specified materials can also be used as electrodes.

[0121] The electrochemical cell 0 has an active area A which corresponds to the area of ​​the membrane 3, the anode 4 and the cathode 5.

[0122] During operation, the first compartment 1 is supplied with a feed 10. The feed 10 is an aqueous solution containing Li+ cations. From an electrochemical perspective, the feed 10 can be considered an anolyte. The feed 10 can be a Li lye from a natural deposit or a material stream resulting from the processing of spent LIB. The concentration of the Li+ cations in the feed 10 (formula letter CF) should be at least 200 wt. ppm, based on the total mass of the feed. Seawater has a lower Li concentration and would therefore have to be concentrated before being used in the process. The feed 10 also contains anions such as sulfate or chloride. The feed 10 also contains impurities. Anions and impurities are not shown in Figure 1. The main component of the feed 10 is water H2O.

[0123] The second compartment is loaded with a lean working medium 12. The lean working medium 12 is water H2O with a low concentration of CMO Li + Cations. The CMO concentration is at least 50 ppm by weight based on the total mass of the lean working medium 12. From an electrochemical perspective, the lean working medium 12 is considered the catholyte.

[0124] The electrochemical cell 0 is also subjected to an electrical voltage U supplied from the voltage source 7. This causes the following:

[0125] First, water electrolysis occurs, in which water (H2O) is electrochemically separated into hydrogen (H2) and oxygen (O2). OH- and hydrogen are formed at the cathode 5. However, the OH- anions cannot cross the membrane 3 and combine with the Li present in the cathodic compartment 2. + -cations to lithium hydroxide (LiOH). At the anode 4, oxygen and H +formed.

[0126] The formation of LiOH in cathodic compartment 2 is maintained by Li+ cations migrating from feed 10 toward cathode 5, driven by the voltage U. They overcome membrane 3 due to its conductivity for Li ions and accumulate in the working medium (membrane electrolysis). This creates a rich working medium 13, which is withdrawn from the second compartment 2. The concentration of Li+ ions in the rich working medium 13 is higher than in the poor working medium 12; CMI > CMO

[0127] In the electrochemical cell 0, water electrolysis, membrane electrolysis of Li + and a synthesis of LiOH.

[0128] During the simultaneous operation of Li+ membrane electrolysis and water electrolysis in the electrochemical cell, lithium hydroxide LiOH and molecular hydrogen H2 are directly produced. The hydrogen is at least partially dissolved; it can also be present in gas bubbles. According to the invention, the lithium hydroxide is concentrated above its solubility. This means that the lithium hydroxide is at least partially present as a solid in the rich working medium 13. Depending on the temperature and the presence of crystallization nuclei, the LiOH precipitates in the second compartment 2 or immediately after the rich working medium 13 is withdrawn. Impurities typically act as crystallization nuclei.

[0129] Feed 10 is enriched with Li by membrane electrolysis +depleted, resulting in wastewater 14. Cw < CF applies. The formula letter c stands for the concentration of Li ions in the wastewater 14, based on the total mass of the wastewater 14. The formula letter CF stands for the concentration of Li ions in the feed 10, based on the total weight of the feed 10.

[0130] Figure 2 shows how LiOH is extracted as the target product 15 from the rich working medium 13.

[0131] For this purpose, a separation device 16 is provided, into which the rich working medium 13 is introduced. The separation device 16 separates the target product from the rich working medium 13

[0132] 15, which has a particularly high concentration of LiOH. The target product also contains water and impurities, depending on the desired target product specifications.

[0133] Since the rich working medium contains 13 LiOH in solid form, the separation apparatus is

[0134] 16 is preferably a solids 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.

[0135] The LiOH-depleted output stream of the separation apparatus 16 is recycled as lean working medium 12 into the second compartment 2 of the electrochemical cell 0.

[0136] As already mentioned, the lean working medium 12 must contain a certain concentration of LiOH (CMo) so that the process in the electrochemical cell 0 starts as desired thanks to a low starting resistance. The CMO should be at least 50 ppm by weight based on the total mass of the lean working medium 12. To ensure the required CMO concentration, the separation apparatus 16 is operated in such a way that it does not completely separate the LiOH from the rich working medium 13. This is particularly easy when using a solids separator, because the dissolved LiOH fractions are left in the working medium and can be recycled into the second compartment 2 with the required starting concentration greater than 50 ppm.

[0137] In addition to lithium hydroxide LiOH, the process also produces hydrogen H2. The hydrogen H2 is at least partially dissolved in the rich working medium 13 and is withdrawn from the second compartment 2 together with the LiOH. Since the hydrogen H2 easily evaporates from the water, no great effort is required to remove it from the rich working medium. Only if the hydrogen H2 is to be used as a second target product is a corresponding second separation device required to separately extract the hydrogen of suitable quality / purity (not shown).

[0138] The water H2O contained in the rich working medium 13 is almost completely recycled as the lean working medium 12. Only the (crystallized) water contained in the target product 15 is lost from the process. It must be added accordingly to the lean working medium 12 (not shown). The water contained in the feed 10 does not enter the circuit between the second compartment 2 and the separation apparatus 16 because the membrane 3 is impermeable to water.

[0139] Try:

[0140] The effects achieved with the invention will now be explained using experiments.

[0141] To perform the electrolysis, the electrolysis cell is first assembled and connected to the anolyte and catholyte tanks. Care is taken to ensure that the inlet and return lines are connected to the same side.

[0142] A round disc with a diameter of 19.5 mm and a thickness of 1 mm was used as the anode and cathode. The material in each case was a titanium expanded metal sheet coated on both sides with IrTi mixed oxide, 12 g Ir / m2, 1 AF D1 .5 mm, from Metakem GmbH, 61250 Usingen, Germany.

[0143] The sampled membranes were also circular discs with a diameter of approximately 25 mm. The membranes were approximately 1 mm thick. The material of the sampled membranes was a LATSP, namely LICGC® PW01 from OHARA GmbH, Hofheim, Germany.

[0144] The electrolysis unit and the corresponding storage tanks are blanketed with nitrogen throughout the entire experiment to prevent the formation of lithium carbonate. Each cell has a separate anolyte and catholyte tank. Each tank is filled with approximately 1 kg of liquid; the exact mass is determined by backweighing. In all experiments, the catholyte was always a 5 mmol / L LiOH solution (equivalent to 120 wt. ppm LiOH). The anolyte is a lithium salt solution in various concentrations and various lithium salts. The starting concentration in each case was 1.0 mol / L LiOH. The exact concentration varies throughout the experiment and is therefore also listed in the diagram of the experiments.

[0145] The experiment is started by switching on the pumps and the desired voltage. The maximum flow rate is 900 mL / minute. Sampling occurs every half hour or at longer intervals as agreed. 3 mL of pre-flow is drawn and discarded. With each sample, the current is recorded, and the pH and conductivity of the sample are determined. The samples are then returned to the appropriate containers to maintain a nearly constant volume.

[0146] After the test, the containers are emptied, and all lines and the membrane are rinsed with deionized water. The cell is disassembled, the membrane is photographed, and SEM images of the catholyte and anolyte sides are taken to document any damage or changes to the membranes. Membrane performance is assessed using the permeability parameters (gLi*mm / m 2 *h) and permeance (g Li / m 2*h) measured. Permeance indicates how much mass of lithium is transported through the membrane per unit area and time. Permeability also takes membrane thickness into account, thus allowing for comparison between different membrane types with varying thicknesses. Both parameters are necessary for a comprehensive description of performance, as extremely thin membranes would enable extremely high permeance. However, if concentration polarization effects occur in the membrane cell, the permeabilities would be incorrectly represented. Considering membrane thickness is then no longer useful, as transport is not limited by the membrane.

[0147] All measured values ​​shown in the examples are subject to a measurement error of approximately + / - 10%, which can be attributed to inaccuracies in the positioning of the electrodes relative to each other, the determination of the thickness of the membrane samples and the concentration determination via conductivity measurements.

[0148] The concentration was determined inline using a conductivity measurement. The calibration curve shown in Figure 3 translates the conductivity into a concentration in the test results.

[0149] Figure 3: Conductivity as a function of the concentration of a LiOH solution (25°C)

[0150] Consequently, at concentrations above approximately 10% LiOH, it is hardly possible to accurately monitor the actual concentration using conductivity measurements.

[0151] First attempt:

[0152] A first attempt to concentrate to greater than 10% LiOH is summarized in Table 2 and Figure 4, whereby the reduced accuracy of the concentration determination via conductivity determination must be taken into account.

[0153] Table 2: Test parameters

[0154] Figure 4: graphical representation of the test results

[0155] The jagged curve of the anolyte conductivity visible in Figure 4 is due to the regular renewal of the anolyte when it has reached a concentration of less than approximately half the starting concentration. After approximately 100 hours, the catholyte had to be replaced once because the cell was leaking. This then led to a significant drop in the concentration and thus the conductivity of the catholyte solution. This experiment demonstrated that this procedure could be used to increase the lithium hydroxide concentration significantly above the starting concentration of the anolyte. The experiment was terminated after approximately 500 hours of operation when the concentration had been increased to approximately 9% lithium hydroxide, as a differentiated evaluation of the lithium hydroxide concentration was not possible. The catholyte had a temperature of 27°C; no solid lithium hydroxide was formed.

[0156] Second try:

[0157] A repeat test with the same specifications as in Table 2 led to the following result:

[0158] Figure 5: graphical representation of the results of the repeat experiment

[0159] Figure 5 also shows the regular renewal of the anolyte solution in the jagged curve of the conductivity measurement in the anolyte. The catholyte conductivity increases over a period of approximately 1000 hours to a limit of approximately 395 to 400 mS / cm, which results from the solubility and electrical properties of a lithium hydroxide solution at a temperature of approximately 25°C. Since, as already described above, the exact concentration cannot be determined via conductivity, a sample was taken after approximately 1010 hours of operation, and the lithium hydroxide content was determined gravimetrically.

[0160] The temperature of the anolyte and catholyte was then raised to 40°C, and the electrolysis was continued. A temperature correction was applied to the conductivity determination, as specified by the instrument manufacturer. At this elevated temperature, the conductivity (with temperature correction) did not increase further, remaining at approximately 400 mS / cm.

[0161] After continuing electrolysis for 48 hours, the saturation limit for lithium hydroxide should be reached at a temperature of 40°C. Therefore, another sample was taken from the catholyte circuit, and the lithium hydroxide content was determined gravimetrically.

[0162] The temperature of both circuits was then increased to 60°C, and electrolysis continued. After approximately another 90 hours, the saturation concentration for this temperature was again expected to be reached, which was to be confirmed by sampling and gravimetric solids content determination. Despite a final increase in temperature to 80°C and continued operation until the desired saturation concentration was reached for the planned period of approximately 110 hours, the experiment could not be completed because a leak occurred in the measuring equipment after approximately 60 hours. A sample was taken to determine the solids content.

[0163] The remaining catholyte was then drained, cooled to room temperature under a nitrogen atmosphere, and allowed to stand for a while, allowing some of the lithium hydroxide to settle as a white deposit from the solution, now kept at 20°C. All concentration determinations were carried out under the exclusion of carbon dioxide and under a nitrogen blanket. The results of the individual concentration determinations are summarized in Table 3. They represent the amount of lithium hydroxide in the solution determined by sampling at the end of each temperature stage. The average permeabilities are calculated from the determined concentrations, the electrolysis duration, and the area of ​​the membrane used.

[0164] Table 3: Lithium hydroxide contents of the various samples

[0165] *The solubilities of LiOH were taken from Table 1.

[0166] Table 3 shows that the LiOH content was increased to approximately 0.1% - 0.3% above the saturation limit. After cooling, solid LiOH * H2O was formed.

[0167] Conclusion:

[0168] The experiments demonstrate that it is possible to drive the process to such an extent that the solubility limit of LiOH in the cell is exceeded. In this way, solid LiOH can be produced using the electrochemical cell alone.

[0169] List of reference symbols

[0170] 0 electrochemical cell

[0171] 1 first compartment

[0172] 2 second compartment

[0173] 3 Membran

[0174] 4 Anode

[0175] 5 Cathode

[0176] 6 first electrical line

[0177] 7 Voltage source

[0178] 8 second electrical line

[0179] 9 not assigned

[0180] 10 Feed

[0181] 11 not assigned

[0182] 12 poor working medium

[0183] 13 rich working medium

[0184] 14 Wastewater

[0185] 15 Target product

[0186] 16 Separator

[0187] H2O water

[0188] H2 hydrogen

[0189] O2 oxygen

[0190] LiOH lithium hydroxide

[0191] OH-OH anions

[0192] Li + Lithium cations

[0193] U electrical voltage

[0194] I electric current

[0195] A active area

[0196] CF concentration LiOH in the feed

[0197] Cw concentration LiOH in wastewater

[0198] CMO concentration LiOH in the lean working medium

[0199] CMI concentration LiOH in the rich working medium

Claims

Patent claims 1. A process for producing hydrogen and lithium hydroxide, comprising the following steps: a) providing a feed containing at least water, Li ions, and impurities, wherein the concentration of Li ions in the feed CF 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 containing water and lithium hydroxide dissolved therein, wherein the concentration of lithium hydroxide in the lean working medium CMO is at least 50 ppm by weight, based on the total weight of the lean working medium; c) providing at least one electrochemical cell, wherein the electrochemical cell has the following features: i. the electrochemical cell comprises a first compartment in which an anode is arranged; ii. the electrochemical cell comprises a second compartment in which a cathode is arranged; iii.the electrochemical cell comprises a membrane which separates the first compartment from the second compartment, wherein the membrane has the area A; iv. the membrane contains an inorganic material which has a conductivity for Li-ions and which is electrically insulating; d) providing at least one electrical voltage source which is connected to the anode via a first electrical line and to the cathode via a second electrical line; e) supplying the first compartment with the feed; f) supplying the second compartment with the lean working medium; g) supplying the electrochemical cell with an electrical voltage U obtained from the electrical voltage source, such that an electrical current / flows between the anode and cathode, wherein the quotient Q of the current intensity of the electrical current / and the area A of the membrane is between 100 A / m. 2 and 500 A / m 2 or between 150 A / m2 and 350 A / m 2 h) withdrawing wastewater containing at least water, Li salts dissolved therein, oxygen, and impurities from the first compartment, wherein the concentration of Li ions in the wastewater Cw based on the total weight of the wastewater is lower than the concentration of Li ions in the feed CF based on the total weight of the feed; i) withdrawing a rich working medium containing water, hydrogen and lithium hydroxide from the second compartment, wherein the concentration of lithium hydroxide in the rich working medium CMI based on the total weight of the rich working medium is greater than the concentration of lithium hydroxide in the lean working medium CMO based on the total weight of the lean working medium, and wherein the concentration of lithium hydroxide in the rich working medium CMI based on the total weight of the rich working medium is greater than the solubility of lithium hydroxide in water at a temperature 7MI , wherein the temperature TMI denotes the temperature of the rich working medium at the time of its withdrawal from the second compartment.

2. Process according to claim 1, characterized in that the rich working medium contains lithium hydroxide as a solid at the time of its withdrawal from the second compartment.

3. Process according to claim 1 or 2, characterized in that the temperature 7MI of the rich working medium at the time of its withdrawal from the second compartment is between 20°C and 60°C.

4. The method according to claim 3, characterized in that the concentration of lithium hydroxide in the rich working medium CMI, based on the total weight of the rich working medium, is greater than 0.1276 kg / kg or greater than 0.138 kg / kg or greater than 0.146 kg / kg, each calculated as LiOH; or that the concentration of lithium hydroxide in the rich working medium CMI, based on the total weight of the rich working medium, is greater than 0.21 kg / kg or greater than 0.231 kg / kg, each calculated as LiOH^F.

5. Process according to one of claims 1 to 4, characterized in that the concentration of lithium hydroxide in the lean working medium CMO is less than 12.8 wt.% based on the total weight of the lean working medium.

6. Process according to one of claims 1 to 4, characterized in that the feed contains anions which are selected from the group consisting of sulfate, carbonate, hydroxide, chloride.

7. Process according to one of claims 1 to 6, characterized in that the feed contains impurities in the form of compounds of elements which are selected from the group consisting of B, Na, Mg, Al, Si, K, Ca, Mn, Fe, Co, Ni, Cu, C. Method according to one of the preceding claims, wherein the inorganic material contained in the membrane has a conductivity for Li-ions measured according to the method described here “impedance spectroscopy” which at a temperature of 23°C is at least 1*10 -5 S / m or at least 5*10 -5 S / m or at least 10*10 -5 S / m and maximum 100*10 -5S / m. Method according to claim 8, characterized in that the inorganic material is a compound of the following stoichiometry (LATP): Lii+xAlxTi2-x(PO4)3 where: 0.1 <x<0.3, wobei bevorzugt gilt x=0.

3. Verfahren nach Anspruch 8, dadurch gekennzeichnet, dass es sich bei dem anorganischen Material um eine Verbindung der folgenden Stöchiometrie (LATSP) handelt: Lil+x+yAlxTi2-xSiyP3-yOl2 where: 0.1 <x<0.3 und 0.2<y<0.

4. Verfahren nach Anspruch 8, dadurch gekennzeichnet, dass es sich bei dem anorganischen Material um eine Verbindung der folgenden Stöchiometrie (LAGTSP) handelt: Lii+x+yAlxTi2-xSiyP3-yOi2 * nGeO2 where: 0 <x<1 und 0<y<1 und 0<n<1 Verfahren nach Anspruch 8, dadurch gekennzeichnet, dass es sich bei dem anorganischen Material um eine Verbindung der folgenden Stöchiometrie (LAGTP) handelt: Lii 4Alo 4(Gei-xTix)i 6 (PÜ4)3 where: 0 <x<1 . Verfahren nach Anspruch 8, dadurch gekennzeichnet, dass es sich bei dem anorganischen Material um eine Verbindung der folgenden Stöchiometrie (LAGP) handelt: Lii+xAlxGe2-x (PÜ4)3 where: x=O or x=0.2 or x=0.

4. Process according to claim 8, characterized in that the inorganic material is a compound of the following stoichiometry (LLTO): Li3xLa ( 2 / 3)-xn(i / 3)-2xTiO3wherein: 0 <x<0.

16. Verfahren nach einem der vorhergehenden Ansprüche mit den zusätzlichen Schritten: k) Bereitstellen eines Trennapparates; l) Abtrennen von Lithiumhydroxid aus dem reichen Arbeitsmedium mit Hilfe des Trennapparates. Verfahren nach Anspruch 15, dadurch gekennzeichnet, dass in dem Schritt I) Separating lithium hydroxide from the rich working medium using the separation apparatus to obtain a product having the following composition: Lithium hydroxide: >56.5 wt% Water: <43.5 wt% Carbon dioxide: <0.35 wt% Sulphur dioxide: <0.01 wt% Chlorine: <0.002 wt% 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, whereby the weight proportions add up to 100% and are based on the total weight of the product.

17. Method according to claim 15 or 16, characterized in that in the step I) Separating lithium hydroxide from the rich working medium with the aid of the separation apparatus; the lean working medium is obtained in such a way that step b) providing a lean working medium containing water and lithium hydroxide dissolved therein, wherein the concentration of lithium hydroxide in the lean working medium CMO, based on the total weight of the lean working medium, is at least 50 ppm by weight; is carried out with the aid of the separation apparatus.

18. A method according to claim 15 or 16 or 17, characterized in that the electrochemical cell and the separation apparatus are provided at the same location.

19. The method according to claim 18, characterized in that at least the process steps i) withdrawing a rich working medium containing water, hydrogen and lithium hydroxide from the second compartment; and I) Separation of lithium hydroxide from the rich working medium using the separation apparatus; this should be done continuously.

20. Method according to one of claims 15 to 19, characterized in that the separation apparatus is a solid-state separator.

21. A method according to claim 20, characterized in that the separating means is selected from the group consisting of the following solid separators: filter, hydrocyclone, settling separator.

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