Production of hydrogen and solid lithium hydroxide

Abstract

The problem addressed by the invention is that of providing a method for producing lithium hydroxide with very high energy efficiency. The method should in particular avoid the use of thermal energy. As a raw material, the method should be able to treat Li-containing water generated during the impregnation of used lithium ion batteries. The LiOH produced by the method has enough high purity, so that the LiOH can be directly used for producing new LIB. The process should achieve high throughput and with low space requirements so that it can be combined with existing processes for reprocessing used LIBs or for producing new LIBs to form a closed, continuous production cycle. The method according to the invention is an electrolytic film method operating using a LiSICon film. A particular aspect of the method is to perform electrolysis up to the precipitation limit of lithium hydroxide.

Description

[0001] Lithium (Li) is, by definition, essential for the production of lithium-ion batteries (LIBs). Due to its high reactivity, lithium does not exist in pure form in nature, but always in bound form. The starting material for LIB production is typically lithium in the form of lithium hydroxide (LiOH) or lithium carbonate (Li2CO3).

[0002] In most natural ore deposits, Li is present in the form of lithium oxide (Li2O) or salts such as lithium sulfate (Li2SO4) or lithium chloride (LiCl). Lithium oxide is a component of ores such as pegmatites, while lithium sulfate and lithium chloride are present in dissolved form in the leachate of Li salt lakes. During the mining process, the extracted lithium compounds are converted into lithium carbonate (Li2CO3) in certain cases. In a further process step, lithium carbonate can be converted into lithium hydroxide by reaction with quicklime or calcium hydroxide. The extraction of Li and its conversion into LiOH are described in:

[0003] 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.

[0004] Rich lithium deposits are known to exist, but producing LiOH from the lithium compounds they contain is very energy-intensive and produces large amounts of wastewater. Similarly, there is a strategic need to break away from dependence on the owners of the deposits.

[0005] One solution to this problem could be to reprocess the material from spent LIBs so that the lithium contained therein can be reused as raw material for new batteries.

[0006] Recycling methods for LIBs have been developed to industrial maturity in the past, but in most cases they target the metals Fe, Ni, Mn, Co, Mg, and Al present therein. Alkali metal Li is generally not recycled because its high reactivity makes it difficult to separate from spent batteries, and it is readily available in sufficient quantities from natural deposits at low cost. For a long time, extracting Li from spent LIBs seemed fundamentally uneconomical.

[0007] However, there is growing social and economic pressure to recover lithium from used LIBs. To achieve this, it is necessary to supply LIB manufacturers with recycled lithium of acceptable quality, so that the process for manufacturing LIBs from recycled Li does not differ from that using mined virgin lithium. Naturally, this must not adversely affect battery quality. Therefore, the recovered Li, especially in the form of LiOH, must meet very strict purity specifications. Furthermore, the process used to recover Li from used batteries must be as energy-efficient as possible. The process should also use minimal water.

[0008] Known methods for recovering lithium from old batteries are summarized in the following documents:

[0009] Pankaj K.Choubey et al.:Advance review on the exploitation of the

[0010] prominent energy-storage element Lithium.Part II:From sea water and

[0011] spent lithium ion batteries(LIBs),Minerals Engineering,volume 110,2017,pages 104-121

[0012] DOI:10.1016 / j.mineng.2017.04.008.

[0013] The “LISM” technology, mentioned only in passing in the aforementioned review article, is the electrolysis of Li-containing water in the presence of so-called LiSICon membranes.

[0014] LiSICon stands for lithium superion conductor. This is a class of inorganic glass-ceramic materials that are electrical insulators but inherently conductive to lithium ions. The transport mechanism for lithium ions stems from the material's crystal structure. In short, the lithium ions "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 initially developed as solid-state electrolytes for lithium ion batteries (LIBs). An overview of the transport mechanism of LiSICon, its crystal structure, and its production is provided in the following literature:

[0015] Palakkathodi Kammampata et al.: Cruising in ceramics–discovering

[0016] 全固态电池的新结构——基础、材料和

[0017] 性能。《离子学》24, 639 - 660(2018)

[0018] DOI: 10.1007 / s11581 - 017 - 2372 - 7 [[ID=~10]]

[0019] 耶杜孔达卢·梅萨拉等人:锂离子

[0020] 全固态锂离子电池导体的最新进展。《美国化学会能源快报》2017年,2卷,12期,2734 - 2751页

[0021] DOI: 10.1021 / acsenergylett.7b00849

[0022] The following literature describes the specific LiSICon stoichiometry:

[0023] 索菲亚·萨菲里奥等人。锂 1.4 铝 0.4 锗 0.4 钛 1.4 (PO4)3有前景

[0024] 用于全固态锂基电池的NASICON结构玻璃陶瓷电解质:揭示三氧化二硼的作用,《欧洲陶瓷学会杂志》,第42卷,第3期,2022年,第1023 - 1032页

[0025] batteries: Unravelling the effect of diboron trioxide, Journal of the

[0026] European Ceramic Society, volume 42, issue 3, 2022, pages 1023 - 1032

[0027] DOI 10.1016 / j.jeurceramsoc.2021.11.014。

[0028] Eongyu Yi et al.Materials that can replace liquid electrolytes in Libatteries:Superionic conductivities in Li 1.7 Al 0.3 Ti 1.7 Si 0.4 P 2.6 O 12 .Processingcombustion synthesized nanopowders to free standing thin films.Journal ofPower Sources,volume 269,2014,pages 577-588,DOI

[0029] 10.1016 / j.jpowsour.2014.07.029.

[0030] The selective conduction of Li ions by LiSICon materials means they 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 propel the Li ions across the LiSICon membrane is voltage. To this end, 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 electrodes in each compartment, the compartment is called either anode or cathode. 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 through to the cathode. As a result, the water in the cathode compartment (catholyte) becomes enriched with Li, while the water on the anode side (catholyte) is depleted of Li. This process is known as membrane electrolysis.

[0031] Membrane electrolysis processes for extracting lithium using LiSICon membranes have been described in the prior art.

[0032] For example, Zhen Li et al. describe a method using weakly lithiated water from the Red Sea as a raw material:

[0033] Zhen Li et al.: Continuous electrical pumping membrane process for seawater lithium mining. Energy Environ. Sci., 2021, 14, 3152 DOI:

[0034] 10.1039 / d1ee00354b.

[0035] Zhen Li's research team used LLTO as a membrane. The target product separated was lithium phosphate (Li3PO4), which is suitable for producing lithium iron phosphate (LFP) battery packs. However, it cannot be directly used to produce LIBs with different cathode materials, such as nickel-manganese-cobalt (NMC) or lithium manganese oxide (NMO).

[0036] Yang et al. attempted to extract metallic lithium directly from seawater with the help of solar energy, LAGP membrane and copper foil.

[0037] Sixie Yang et al.:Lithium Metal Extraction from Seawater.Joule,volume2,issue 9,2018,pages 1648-1651,DOI

[0038] 10.1016 / j.joule.2018.07.006.

[0039] US2016 / 0201163 A1 describes the separation of Li ions from salt water such as seawater by means of a LiSICon membrane. The membrane materials proposed are specifically Li3N, 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).

[0040] WO 2019055730 A1 also relates to lithium separation using a LiSICon membrane. LLTO, LAGP, and LATP are specifically mentioned. The LiSICon material can be applied to a support structure. The chemical properties of the support structure are not described in detail. Similarly, there is little description of how the LiSICon is applied to the support structure. The target product to be separated is lithium ions.

[0041] US9222148B2 also discloses separating lithium hydroxide by electrolysis on a LiSICon membrane and subsequent precipitation of lithium hydroxide hydrate. A disadvantage of this method is that it requires an energy-intensive evaporation step to precipitate the lithium hydroxide.

[0042] US20120103826 A1 describes the electrodialytic separation of lithium hydroxide from contaminated streams using a LiSICon membrane. To achieve high purity, LiOH is precipitated from brine. This exploits the lower solubility of LiOH in water compared to foreign salts. The precipitate is then redissolved and introduced into an electrodialysis cell. The LiOH concentration in the catholyte of the electrodialysis cell is not specified in US20120103826 A1. The catholyte is diluted with water. A disadvantage of this method is the requirement for laborious crystallization prior to electrolysis, and the heat of crystallization is lost due to the redissolution of the precipitate. Therefore, this method is technically laborious and energy-intensive.

[0043] In addition to the use of ceramic LiSICon membranes, electrolytic processes for lithium separation using organic ion exchange membranes are also known.

[0044] For example, EP 3805428 A1 describes the electrolytic production of lithium hydroxide. In addition to the electrolysis, the lithium is electrochemically converted into lithium hydroxide. To obtain the necessary reactants, water undergoes a simultaneous electrochemical decomposition. This is done using a bipolar three-compartment cell with an ion exchange membrane. Commercially available AVV, 902, FAB, FKB and CMB ion exchange membranes. The chemical nature of these ion exchange membranes is not disclosed in EP 3805428 A1, but they are most likely organic membrane materials. The three-compartment cell operates in an acidic medium. In particular, water containing a lithium salt such as lithium sulfate (Li2SO4) or lithium chloride (LiCl) is used as the feed.

[0045] US10036094 B2 discloses the production of lithium hydroxide from aqueous lithium sulfate and / or lithium bisulfate solutions in a two-stage electrodialysis / electrolysis process with simultaneous water splitting. The first stage employs a two-compartment electrochemical cell, and the second stage employs a three-compartment cell. The cell is equipped with an ion exchange membrane. The chemical composition of the ion exchange membrane is not given. The following commercial membranes are mentioned: FAB, ACM, MV, 324 and AHA.

[0046] The main drawback of polymer membranes is their permeability to water. This results in dilution of the anolyte with water from the catholyte. This then requires dehydration of the target product, which in turn consumes thermal energy or limits the plant's location to areas with sufficient sunlight.

[0047] Besides their water permeability, another major disadvantage of organic ion exchange membranes is that they have lower ion selectivity than inorganic LiSICon materials: they allow not only Li + Pass, and allow Na + In addition to the purity of the target product, the electrical efficiency of the process is also affected: if non-ion selective membranes are used for electrolysis, the unwanted Na + The transmission to the second compartment will also consume valuable energy. In addition, when it reaches the second compartment, Na + The ions are converted into unwanted byproducts through unintended electrochemical processes, which reduces the energy efficiency of the process based on the yield of the target product, Li.

[0048] Finally, organic films have a strong affinity for Mg 2+ and Ca 2+ Organic ion exchange membranes are sensitive to the presence of divalent cations. Over time, these cations can poison the membrane, limiting the useful life of the membrane.

[0049] Glass-ceramic LiSICon materials guarantee better ion selectivity. However, the stability of LiSICon membranes towards impurities remains a significant problem for industrial practice. For example, Li-containing + Water contains other cations, especially such as Na + and K + , which causes lasting damage to the LiSICon material: these cations appear to occupy defects in the crystal structure, which causes Li + Cation transport through the membrane virtually ceases. The electrochemical cell's service life then expires. The high cost of LiSICon materials means that recovering lithium from LIBs is uneconomical if the membrane's service life is short. Furthermore, the brine from Li salt lakes has a naturally high sodium content, making it incompatible with conventional LiSICon membranes. Therefore, lithium from the salt lakes undergoes an energy-intensive thermal separation process and / or a stepwise process using large amounts of water, during which the lithium is dissolved and then recrystallized. While water here can be evaporated by solar radiation, water for dissolving LiCl is scarce in the deserts of South America, making this route extremely difficult there.

[0050] Another practical issue is the high specific resistance of the LiSICon material. This results in a high ohmic internal resistance in the electrochemical cell, which means that the method requires a correspondingly high amount of electrical energy. In theory, the membrane could be made thinner to reduce this. However, the material's low thickness results in a short lifespan in aggressive environments.

[0051] Based on this prior art, the problem addressed by the present invention is to provide a very energy-efficient method for producing lithium hydroxide. The method should, in particular, be carried out without the use of thermal energy. As a raw material, the method should be able to process the Li-containing water produced when digesting used lithium-ion batteries. The LiOH produced by the method should have a sufficiently high purity that it can be used directly in the production of new LIBs. The method should achieve a high throughput and have a low space requirement, so that it can be combined with existing methods for reprocessing used LIBs or for producing new LIBs to form a closed, continuous production cycle. Finally, the method should require as little fresh water as possible and produce very little wastewater.

[0052] This problem is solved by a method according to claim 1 .

[0053] Therefore, the present invention provides a method for producing hydrogen and lithium hydroxide, comprising the steps of:

[0054] a) providing a feed comprising at least water, Li ions and impurities, wherein the concentration of Li ions in the feed is C F at least 200 ppm by weight or between 500 ppm by weight and 140 000 ppm by weight, based in each case on the total weight of the feed,

[0055] b) providing a lean working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration of lithium hydroxide in the lean working medium is C based on the total weight of the lean working medium. M0 is at least 50 ppm by weight;

[0056] c) providing at least one electrochemical cell, wherein the electrochemical cell has the following characteristics:

[0057] i) the electrochemical cell comprises a first compartment in which an anode is disposed;

[0058] ii) the electrochemical cell comprises a second compartment in which a cathode is disposed;

[0059] iii) The electrochemical cell comprises a membrane separating the first compartment from the second compartment, the membrane

[0060] has an area A;

[0061] iv) the membrane comprises an inorganic material having Li ion conductivity and being electrically insulating;

[0062] 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;

[0063] e) filling the first compartment with the feed;

[0064] f) filling the second compartment with the lean working medium;

[0065] g) charging the electrochemical cell with a voltage U taken from the 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 between 100 A / m 2 and 500A / m 2 Between or 150A / m 2 and 350A / m 2 between;

[0066] h) taking out 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 is C based on the total weight of the wastewater. W is lower than the concentration C of Li ions in the feed based on the total weight of the feed F ;

[0067] i) taking out 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 is C based on the total weight of the rich working medium. M1 Greater than the concentration C of lithium hydroxide in the lean working medium M0 , and based on the total weight of the rich working medium, the concentration of lithium hydroxide in the rich working medium C M1 Greater than at temperature T M1 The solubility of lithium hydroxide in water at a temperature T M1 refers to the temperature of the rich working medium when it is taken out from the second compartment.

[0068] The process according to the invention is an electrolytic membrane process operating with a LiSICon membrane.

[0069] An important aspect of the method according to the invention is that the selective separation of lithium by the membrane and the electrolysis of water are carried out simultaneously in the cell. In the electrolysis of water, water (H2O) is electrochemically decomposed into H2 and O2. At the cathode, OH is formed. - and hydrogen. However, OH - Anions cannot pass through the LiSICon membrane and are unable to interact with the Li + The cations combine to form lithium hydroxide LiOH. At the anode, oxygen and H + .

[0070] Simultaneous Li-ionization in an electrochemical cell with a LiSICon membrane +Membrane separation and water electrolysis thus result in the direct formation of lithium hydroxide (LiOH) and molecular hydrogen (H2). Both are dissolved in water. The water containing LiOH and H2 is removed from the cathode compartment of the battery. The LiOH is separated from the water. This makes it possible to extract the LiOH, which, due to the selective migration of lithium ions through the membrane, is of sufficient purity for battery production.

[0071] The hydrogen that escapes can be collected and used in the hydrogen economy. If the electrochemical cell is operated with green electricity, the CO2 footprint of this method is also small.

[0072] The feed required for the combination of Li separation and water electrolysis is Li + Cationic water. Such water is produced during the reprocessing of used LIBs or using Li brines from natural deposits.

[0073] The key aspect of the process is to carry out the electrolysis up to the precipitation limit of lithium hydroxide and beyond: this means that the concentration of lithium hydroxide in the rich working medium, C, is based on the total weight of the rich working medium. M1 The solubility of lithium hydroxide in water is greater than that of lithium hydroxide. Therefore, as long as the necessary crystallization nuclei are present, lithium hydroxide can be precipitated as a solid in the cathode liquid. Since these crystallization nuclei are always present in the form of small amounts of impurities, at least a portion of the LiOH is precipitated as a solid in the rich working medium (catholyte).

[0074] The moment at which the lithium hydroxide in the catholyte precipitates as a solid depends on the operating conditions of the cell and the presence of crystallization nuclei: the lithium hydroxide may already have precipitated as a solid in the second compartment, or it may precipitate only immediately after the removal of the rich working medium, i.e., only outside the cell. According to the invention, the rich working medium removed from the second compartment always contains solid lithium hydroxide.

[0075] Preferably, the rich working medium contains solid lithium hydroxide when it is withdrawn from the second compartment.

[0076] Solid lithium hydroxide best refers to lithium hydroxide in crystalline form. Since lithium hydroxide crystals can also intercalate with water, lithium hydroxide can also exist in the form of a gel. In a gel, lithium hydroxide forms the solid phase, while water forms the liquid phase. Gel formation is also determined by residual impurities in the second compartment. This means that the precipitation of lithium hydroxide in the form of a gel depends on the thermodynamic conditions in the second compartment and the concentration of lithium hydroxide and impurities therein. Therefore, for the purposes of this invention, a gel containing solid lithium hydroxide and liquid water is also considered a solid. Therefore, the term "solid" encompasses both crystalline forms and gels.

[0077] Based on the total weight of the rich working medium, the concentration of lithium hydroxide in the rich working medium C M1 Greater than at temperature T M1When the solubility of lithium hydroxide in water reaches the lower limit, the precipitation limit of lithium hydroxide in the second compartment is reached, wherein the temperature T M1 It refers to the temperature of the rich working medium when it is taken out from the second compartment.

[0078] 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 takes into account the temperature T of the rich working medium when it is taken out of the second compartment. M1 Temperature T M1 The optimum is 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 to cool the rich working medium to T immediately before or during removal. M1 However, this does not always make sense energetically.

[0079] The solubility of lithium hydroxide in water actually depends on the purity of the water. If it contains impurities, these act as crystallization nuclei and promote the precipitation of lithium hydroxide.

[0080] Finally, the lithium hydroxide concentration will also differ whether it is calculated as its anhydride (LiOH) or its monohydrate (LiOH·H2O).

[0081] This has obviously led to inconsistencies in the reported solubility of lithium hydroxide in scientific literature or patent applications.

[0082] Monnin and Dubois provide a comprehensive overview of the solubility of lithium hydroxide in water:

[0083] Christophe Monnin and Michel Dubois: Thermodynamics of the LiOH+H2OSystem.Chem.Eng.Data 2005,50,4,1109-1113DOI

[0084] 10.1021 / je0495482

[0085] Additionally, Monnin and Dubois performed mathematical interpolation of values ​​known from the literature.

[0086] Table 1 shows the solubility of lithium hydroxide in water at relevant temperatures given by different authors:

[0087] Table 1: Solubility of LiOH in water

[0088]

[0089] *Values ​​calculated based on the monohydrate according to Ullmann and Kirk Othmer, the remaining values ​​are calculated based on the anhydride.

[0090] The values ​​shown in Table 1 are derived from the following literature sources:

[0091] Dittmar:DOI https: / / doi.org / 10.1016 / 0016-0032(89)90312-8

[0092] D1:US2012103826 A1

[0093] S&M:DOI https: / / doi.org / 10.1021 / je60015a018

[0094] Xie et al.: DOI https: / / doi.org / 10.1016 / j.seppur.2023.123972

[0095] M&D:DOI https: / / doi.org / 10.1021 / je0495482

[0096] KirkOthmer:DOI https: / / doi.org / 10.1002 / 0471238961.1209200811011309.a01.pub2

[0097] Ullmann:https:2 / 14356007.a15_393.pub2

[0098] For T of 20℃ to 60℃ M1 The required temperature range is based on the total weight of the rich working medium and the concentration of lithium hydroxide in the rich working medium C M1 Preferably higher than 0.1276 kg / kg (according to Table 1, this is the minimum 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, C, is based on the total weight of the rich working medium. M1 Higher than 0.138 kg / kg or higher than 0.146 kg / kg. These values ​​are understood to be calculated in the form of LiOH anhydride. If the concentration is determined in the form of lithium hydroxide monohydrate, the concentration of lithium hydroxide in the rich working medium C M1 Should be higher than 0.23kg / kg or higher than 0.256kg / kg.

[0099] On the other hand, the concentration of lithium hydroxide in the lean working medium, C, is based on the total weight of the lean working medium. M0Should be less than 12.8 wt %. This ensures that LiOH has not been introduced into the second compartment in solid form. The lower limit of the LiOH concentration in the lean working medium is 50 ppm. If this is not the case, the reaction will not initiate or proceed.

[0100] With respect to the description of the solubility of lithium hydroxide in water, it should be emphasized that the cell does not have to be operated exactly at the solubility limit. It is expected that the cell will be operated above the precipitation limit in order to precipitate a particularly large amount of LiOH in solid form. 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 will no longer be possible to pump it out of the second compartment. Therefore, the LiOH concentrations shown in Table 1 correspond to C M1 The upper limit is determined by the equipment configuration of the plant in which the method according to the invention is to be carried out. In particular, the structural design of the conveying means (means of conveyance) for removing the rich working medium from the second compartment and conveying it to the downstream separation device is crucial for the upper limit. When implementing the method according to the invention, a separation device is used to separate LiOH from the rich working medium. Bottlenecks in the conveying means and in the cell and pipe connections may become clogged with the crystallized product and thus also limit C. M1 The technically manageable upper limit.

[0101] Since inorganic membranes are insensitive to foreign ions, the feed may contain anions selected from sulfate, carbonate, hydroxide and chloride.

[0102] 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, C. The alkali and alkaline earth metals listed are elements found in natural deposits along with lithium, while the other metals mentioned are used as conductive or cathode materials in LIBs and are therefore present in the feed obtained from the reprocessing of used LIBs. Carbon is also present in the material streams that can be recovered from the reprocessing of used LIBs and originates from polymer components of battery cells, such as films, separators, adhesives, or sealants.

[0103] According to the present invention, membranes composed of inorganic materials are used. This allows the desired ion selectivity to be achieved, unlike with polymer membranes. The membranes are preferably composed entirely of inorganic materials. Composite membranes containing only inorganic materials as a coating on a support material, or in which inorganic materials are dispersed in different types of matrix materials, have proven to be a poor approach.

[0104] In order for this method to work, the inorganic material must conduct Li ions and at the same time act as an electrical insulator. The specific conductivity g (electrical conductivity) of the electrons 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 -16 S / m. Therefore, from the perspective of electron conduction, inorganic materials are classified as non-conductors.

[0105] The specific conductivity of the inorganic material to 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 not more than 100×10 -5 S / m. The Li conductivity of the material was measured by impedance spectroscopy. The measurement was performed as follows:

[0106] The measuring device comprises two cylindrical electrodes with the sample arranged between them.To ensure optimal contact with the electrodes and a reproducible contact pressure, a weight is placed on the sample.

[0107] A potentiostat (Zahner-Elektrik I. Zahner-Schiller GmbH & Co. KG, Kronach-Gundelsdorf, Germany) was connected to the electrodes and controlled via Thales software (Zahner). Measurements were performed in the frequency range of 1 Hz to 4 MHz and at an amplitude of 5 mV using samples that had been polished and sputtered onto a thin conductive gold layer.

[0108] The measurement results were presented in the form of Nyquist plots and evaluated using analysis software (Zahner). The resistance was read at the maximum of the Nyquist plot. The formula σ = (h·10 4 ) / (R·π / 4·d 2 ) Calculate the specific ionic conductivity σ [mS / cm], where h is the sample height in mm, R is the measured resistance in Ω, and d is the sample diameter in mm.

[0109] LiSICon is preferably used as the inorganic material. LiSICon materials are glass-ceramic substances that conduct lithium ions and simultaneously act as an electrical insulator. For the purposes of the present invention, all known LiSICon materials can, in principle, be used as the inorganic material. Known LiSICon materials meet the requirements for conductivity and ionic conductivity specified above for inorganic materials.

[0110] For example, the material LiSICon lithium aluminum titanium phosphate (LATP) can be used. Thus, in one variant of the invention, the inorganic material is a compound with the following stoichiometry:

[0111] Li 1+x Al x Ti 2-x (PO4)3

[0112] Wherein: 0.1≤x≤0.3, wherein preferably x=0.3.

[0113] 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 with the following stoichiometry:

[0114] Li 1+x+y Al x Ti 2-x Si y P 3-y O 12

[0115] Where: 0.1≤x≤0.3 and 0.2≤y≤0.

[0116] In a particularly preferred development of the invention, LATSP is used which additionally contains germanium. LAGTSP is available, for example, from OHARAGmbH, Hofheim, Germany under the product name AG01 obtained.

[0117] The stoichiometry of LAGTSP is:

[0118] Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 *nGeO2

[0119] Where 0≤x≤1 and 0≤y≤1 and 0≤n≤1.

[0120] 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 with the following stoichiometry:

[0121] Li 1+x Al x Ge 2-x (PO4)3

[0122] Wherein: x=0 or x=0.2 or x=0.4.

[0123] However, particular preference is given to using LiSICon which is derived from lithium aluminum germanium phosphate (LAGP) but which additionally contains titanium. This is known as LAGTP.

[0124] Thus, in a preferred variant of the invention, the inorganic material is a compound having the following stoichiometry:

[0125] Li 1.4 Al 0.4 (Ge 1-x Ti x ) 1.6 (PO4)3

[0126] Where: 0≤x≤1.

[0127] As an alternative to the phosphates mentioned above, the oxidic LiSICon material lithium lanthanum titanium oxide (LLTO) can be used. Thus, in one variant of the invention, the inorganic material is a compound with the following stoichiometry:

[0128] Li 3x La (2 / 3)-x□(1 / 3)-2x TiO3

[0129] Where: 0≤x≤0.16.

[0130] The lithium hydroxide is present in the rich working medium and is removed from the second compartment together with it. In order to be able to utilize the lithium hydroxide, it is necessary to separate it from the rich working medium. A separation device is provided for this purpose. Therefore, a preferred development of the present invention includes the following additional method steps:

[0131] k) providing separation equipment;

[0132] 1) Separating lithium hydroxide from the rich working medium by means of the separation device.

[0133] The process is preferably operated in such a way that the separation device separates a product having the following composition:

[0134]

[0135] Parts by weight add up to 100% and are based on the total weight of the product. This type of product is battery grade LiOH and can be used directly in the production of LIBs.

[0136] The product separated in the separation device contains solid lithium hydroxide. The product preferably meets the above-mentioned specifications so that it can be used directly as battery-grade LiOH to produce new LIBs. However, the separated product is not pure LiOH; the principle of its formation means that the separated product will always contain water, which is trapped in the LiOH crystals (crystallization water / internal water). However, the water content of the separated product is less than 43.5% by weight and therefore meets battery-grade specifications. At this water content, the separated product is a crystalline solid rather than a gel.

[0137] The working medium, which has been depleted of LiOH in the separation device, is returned to the electrochemical cell as lean working medium, where it is recharged. Thus, the working medium is recirculated within a closed system. The resulting working medium is recirculated between the second compartment and the separation device. This recirculation of the working medium saves both fresh water supply and wastewater treatment.

[0138] It is important that the lean working medium is not completely free of LiOH, but rather has a certain minimum concentration C of about 50 wt ppm. M0 If this is not the case, the process in the cell cannot be maintained continuously. Therefore, the separation device does not completely separate the LiOH present in the rich working medium, but leaves a residual concentration in the working medium. The separation device preferably separates only solid LiOH and leaves dissolved LiOH in the working medium as an initial concentration C M0 .

[0139] Therefore, a preferred development of the invention comprises the following additional method steps:

[0140] 1) separating lithium hydroxide from the rich working medium by means of a separation device to obtain a lean working medium,

[0141] The steps

[0142] b) providing a lean working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration of lithium hydroxide in the lean working medium is C based on the total weight of the lean working medium. M0 is at least 50 ppm by weight;

[0143] With the help of separation equipment.

[0144] In order to enable the recycling of the working medium between the separation device and the second compartment, it makes sense to install the two devices in the same location. The same location should be understood to mean an integrated production facility. Therefore, the electrochemical cell and the separation device are part of the integrated facility. The closed recycling of the working medium allows the electrochemical cell and the separation device to be installed in the same location and operate continuously. The method is preferably directly incorporated 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 method with a battery recycling plant and output the obtained LiOH.

[0145] It is also conceivable that the separation device is located at a different location away from the electrochemical cell. However, in this case, the working medium must be transported between the cell and the separation device. However, from an energy point of view, this is of little significance.

[0146] Preferably, at least the electrochemical cell is 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 flows in as lean working medium and flows out 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 in batch operation.

[0147] Therefore, in a preferred embodiment of the method, it is envisaged to carry out at least the following method steps continuously

[0148] i) removing a rich working medium comprising water, hydrogen and lithium hydroxide from the second compartment;

[0149] and

[0150] 1) Separating lithium hydroxide from the rich working medium by means of a separation device.

[0151] Since LiOH accumulates in solid form in the method according to the 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. Therefore, the method described herein primarily requires electrical energy to operate the electrochemical cell and secondary electrical energy to transport the material stream. Therefore, the method can preferably be operated using green electricity. Description of the drawings:

[0152] The present invention will now be described in detail with reference to the process flow diagram. In the figure provided for this purpose:

[0153] Figure 1 :Simultaneous Li + Functional principles of membrane electrolysis and water electrolysis;

[0154] Figure 2 : Shows the functional principle of recirculation between electrochemical cells and separation equipment.

[0155] The electrochemical cell 0 required to perform the method 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. Arranged in the first compartment 1 is an anode 4. Arranged in the second compartment 2 is a cathode 5. Therefore, 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.

[0156] 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 polarity of the voltage source 7 is selected such that the positive pole of the voltage source 7 is connected to the anode 4 and the negative pole of the voltage source 7 is connected to the cathode 5.

[0157] The electric current I flows through the two electrical leads 6 and 8 and through the voltage source 7. Since the membrane 3 acts as an electrical insulator, there is no electrical short circuit between the two electrodes 4 and 5 through the membrane 3.

[0158] The membrane 3 is a flat plate membrane made entirely of LiSICon material. The anode 4 is a metal flat plate made of titanium, niobium or tantalum. The cathode 5 is also a metal flat 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 have the same shape and can be rectangular or circular. Figure 1 This is not obvious from the side view. Expanded metals, meshes or nets of specific materials can also be used instead of metal plates as electrodes.

[0159] The electrochemical cell 0 has an active area A corresponding to the surface areas of the membrane 3 , the anode 4 and the cathode 5 .

[0160] During operation, the first compartment 1 is filled with feed 10. The feed 10 is a material containing Li + From an electrochemical point of view, the feed 10 is considered to be the anolyte.

[0161] The feed 10 can be a Li leachate from a natural deposit or a material stream generated by reprocessing used LIBs. Based on the total mass of the feed, the Li content in the feed 10 is + The concentration of cations (formula symbol c F ) should be at least 200 ppm by weight. Seawater has a low Li concentration and therefore must first be concentrated before it can be used in the process. Feed 10 also contains anions such as sulfate or chloride. Feed 10 also contains impurities. Anions and impurities are not shown in FIG. Figure 1 The main component of feed 10 is water H2O.

[0162] The second compartment is filled with a lean working medium 12. The lean working medium 12 is a medium with a low concentration of C M0 Li + Cationic water H2O. Based on the total mass of the lean working medium 12, the concentration c M0 From an electrochemical point of view, the lean working medium 12 is considered to be a catholyte.

[0163] The electrochemical cell 0 is also charged with a voltage U taken from the voltage source 7. This has the following effects:

[0164] First, water electrolysis occurs, where water (H2O) is electrochemically decomposed into hydrogen (H2) and oxygen (O2). At the cathode 5, OH is formed. -and hydrogen. However, OH - The anions cannot pass through the membrane 3 and react with the Li + The cations combine to form lithium hydroxide (LiOH). At the anode 4, oxygen and H + .

[0165] The Li from feed 10 is driven by voltage U + The cations migrate to the cathode 5 to maintain the formation of LiOH in the cathode compartment 2. They pass through the membrane 3 by virtue of the membrane's Li ion conductivity and accumulate in the working medium (membrane electrolysis). This results in the formation of a rich working medium 13, which is discharged from the second compartment 2. The Li in the rich working medium 13 + The concentration of ions is greater than that in the lean working medium 12, so c M1 >c M0 .

[0166] Therefore, water electrolysis, Li + The membrane electrolysis and LiOH synthesis are carried out simultaneously in an electrochemical cell.

[0167] Simultaneous Li + Membrane electrolysis and water electrolysis thus directly form lithium hydroxide LiOH and molecular hydrogen H2. The hydrogen gas at least partially dissolves; it can also be present in the form of bubbles. According to the present invention, the lithium hydroxide is concentrated above its solubility. This means that the lithium hydroxide is at least partially present in solid form in the rich working medium 13.

[0168] Depending on the temperature and the presence of crystallization nuclei, LiOH is precipitated already in the second compartment 2 or immediately after removal of the rich working medium 13. Impurities generally serve as crystallization nuclei.

[0169] Due to membrane electrolysis, the feed of 10 Li + is reduced, producing wastewater 14. Therefore, c W <c F Here, the formula symbol c W represents the concentration of Li ions in the wastewater 14 based on the total mass of the wastewater 14. Here, the formula symbol c F represents the concentration of Li ions in the feed 10 based on the total mass of the feed 10.

[0170] Figure 2 Depicts how LiOH is extracted as target product 15 from the rich working medium 13 .

[0171] For this purpose, a separation device 16 is provided, into which the rich working medium 13 is fed. 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.

[0172] Since 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.

[0173] The LiOH-depleted output stream from the separation device 16 is recycled as lean working medium 12 to the second compartment 2 of the electrochemical cell 0 .

[0174] As mentioned previously, the lean working medium 12 needs to have a certain LiOH concentration C M0 , so that the process in the electrochemical cell 0 can be started in a desired manner with a low starting resistance. Based on the total mass of the lean working medium 12, the concentration c M0 Should be at least 50 ppm by weight. To ensure the required concentration C M0 , the separation device 16 is operated so that not all of the LiOH is separated from the rich working medium 13. This is particularly easy when using a solid separator, because the dissolved part of the LiOH is retained in the working medium by the solid separator and can be recycled to the second compartment 2 at the desired starting concentration of more than 50 ppm.

[0175] In addition to lithium hydroxide LiOH, the process also produces H 2 . Hydrogen H 2 is at least partially dissolved in the rich working medium 13 and is removed from the second compartment 2 together with the LiOH.

[0176] Since hydrogen H2 is easily degassed from water, it can be removed from the rich working medium without much effort. Only when hydrogen H2 is used as the second target product is a corresponding second separation device provided, which is used to obtain hydrogen (not shown) with appropriate quality / purity.

[0177] The water H O present in the rich working medium 13 is recycled as completely as possible as the lean working medium 12. Only the water (water of crystallization) present in the target product 15 is lost from the process. This must be replenished in the lean working medium 12 as needed (not shown). The water in the feed 10 is not ultimately recycled between the second compartment 2 and the separation device 16 because the membrane 3 is impermeable to water.

[0178] experiment:

[0179] The effects achieved by the present invention will now be elucidated with reference to experiments.

[0180] To carry out the electrolysis, first assemble the electrolysis cell and connect the anolyte and catholyte containers. Care should be taken here to ensure that the inflow and return are connected on the same side in each case.

[0181] In each case, the anode and cathode used were disks with a diameter of 19.5 mm and a thickness of 1 mm. The material in each case was a titanium porous metal sheet coated on both sides with an IrTi mixed oxide, 12 g Ir / m 2 , 1AF D 1.5 mm, from Metakem GmbH, 61250 Usingen, Germany.

[0182] The sampled membrane was also a disk with a diameter of about 25 mm. The membrane thickness was about 1 mm. The material of the sampled membrane was LATSP, a product from Ohara GmbH, Hofheim, Germany. PW01.

[0183] The electrolysis vessel and the corresponding reservoir vessel were blanketed with nitrogen for the entire duration of the process to prevent the formation of lithium carbonate. Each cell had a separate anolyte container and a separate catholyte container. Each container was filled with approximately 1 kg of liquid; the exact mass was determined by reweighing. In all experiments, the catholyte was always a 5 mmol / L LiOH solution (corresponding to 120 wt ppm LiOH). In each case, the anolyte was a lithium salt solution with various lithium salts at different concentrations. In each case, the starting concentration was 1.0 mol / L LiOH. The exact concentrations varied during the experiment and are therefore also shown in the experimental figures.

[0184] The experiment begins after the pump is activated and the required voltage is applied. The maximum flow rate is 900 mL / minute. Samples are collected every half hour, or at longer intervals by agreement. The first 3 mL of sample collected is discarded. For each sample collected, the power drawn is recorded and the pH and conductivity of the sample are measured. The sample is then returned to an appropriate container to maintain a nearly constant volume.

[0185] At the end of the experiment, the container was emptied and all leads and membranes were rinsed with demineralized water. The cell was disassembled, the membrane was photographed, and SEM images of the catholyte and anolyte sides were recorded to document any damage or changes to the membrane.

[0186] Membrane performance is measured by the parameter permeability (g Li*mm / m 2 *h) and permeance (g Li / m 2*h). The permeability indicates how much mass of lithium is transported through the membrane per unit membrane area and per unit time. The permeability coefficient also takes into account the membrane thickness and therefore also allows the comparison of different membrane types with different thicknesses. In order to fully describe the performance, both are needed, because very thin membranes will allow very high permeabilities, but if concentration polarization effects are present in the membrane cell, the permeability coefficient will not accurately reflect the actual situation. Taking the membrane thickness into account will no longer serve any useful purpose, because the transport will not be limited by the membrane.

[0187] All measured values ​​shown in the examples are subject to a measurement error of approximately ±10%, which is caused by inaccuracies in the relative positioning of the electrodes, inaccuracies in the thickness determination of the membrane samples, and inaccuracies in the concentration determination by conductivity measurement.

[0188] The concentration is determined by measuring the conductivity online. Figure 3 The calibration curve shown in was converted to concentration.

[0189] Figure 3 : Relationship between conductivity and LiOH solution concentration (25℃).

[0190] However, this does mean that at concentrations above approximately 10% LiOH, it is almost impossible to accurately monitor the actual concentration via conductivity measurement.

[0191] First experiment:

[0192] Table 2 and Figure 4 A first experiment attempting to increase the concentration to more than 10% LiOH is summarized in ; here the reduced accuracy of the concentration determination by conductivity measurement must be taken into account.

[0193] Table 2: Experimental parameters

[0194] Membrane material LATSP(Ohara) Film thickness [mm] 2.0 Film thickness [mm] 100 <![CDATA[Membrane area [cm 2 > 70.88 Voltage [V] 6.0 Current yield [%] 94％ <![CDATA[Permeability (g Li / (m 2 ·h))]]> 8.11 Electrolysis time [h] 493 Temperature [℃] 24 to 27

[0195] Figure 4 : Experimental results in graphical form.

[0196] Figure 4The sawtooth course of the anolyte conductivity evident in the experiment is due to the regular renewal of the anolyte when it reaches a concentration of less than about half of the starting concentration. After about 100 hours, the catholyte had to be replaced due to cell leakage. This then led to a sharp drop in the concentration of the catholyte solution and therefore the conductivity. The experiment showed that, using this operating procedure, the lithium hydroxide concentration could be increased to a level far above the starting concentration of the anolyte. The experiment was terminated after a run time of about 500 hours, at a lithium hydroxide content of about 9%, as a differential assessment of the lithium hydroxide concentration was no longer possible. The catholyte had a temperature of 27°C and no solid lithium hydroxide was formed.

[0197] Second experiment:

[0198] The experiment was repeated using the same protocol as in Table 2, and the following results were obtained:

[0199] Figure 5 : Results of repeated experiments in graphical form.

[0200] Also in Figure 5 The regular renewal of the anolyte solution is evident in the jagged course of the anolyte conductivity measurements. The catholyte conductivity increases over a period of approximately 1000 hours to a limit of approximately 395 to 400 mS / cm, which is derived from the solubility and electrical properties of lithium hydroxide solution at a temperature of approximately 25°C. As mentioned above, since 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.

[0201] The temperature of the anolyte and catholyte was then raised to 40°C and the electrolysis continued. In the conductivity determination, the temperature correction specified by the measuring device manufacturer was applied. At this elevated temperature, the conductivity (temperature-corrected) did not increase further and therefore remained at approximately 400 mS / cm.

[0202] After a further 48 hours of electrolysis, the saturation limit of lithium hydroxide should be reached at a temperature of 40° C. Therefore, another sample is taken from the catholyte circuit and its lithium hydroxide content is determined gravimetrically in this manner.

[0203] The temperature was then raised to 60°C for both cycles, and electrolysis was continued. After approximately 90 hours, the saturation concentration at this temperature was to be reached again, which was to be confirmed by sampling and gravimetric determination of the solids content. During the final temperature increase to 80°C and continued operation for the planned period of approximately 110 hours until the desired saturation concentration was reached, a leak developed in the measuring device after approximately 60 hours, preventing the completion of the experiment. Samples were taken to determine the solids content.

[0204] The remaining catholyte was then drained, cooled to room temperature under a nitrogen atmosphere and allowed to stand for a period of time to allow some of the lithium hydroxide in the solution, now maintained at 20° C., to settle as a white precipitate. All concentration determinations were performed with exclusion of carbon dioxide and under a nitrogen blanket.

[0205] The results of the individual content determinations are summarized in Table 3. They reflect the amount of lithium hydroxide in the solution at the end of each temperature level, as determined by sampling. The average permeability coefficient was calculated from the determined content, the electrolysis time, and the area of ​​the membrane used.

[0206] Table 3: Lithium hydroxide content of different samples

[0207]

[0208] *The solubility of LiOH was obtained from Table 1.

[0209] As can be seen from Table 3, the LiOH content reaches about 0.1-0.3% above the saturation limit. Cooling results in the formation of solid LiOH·H2O.

[0210] in conclusion:

[0211] The experiments demonstrated that it is possible to run the process beyond the solubility limit of LiOH in the battery, meaning that solid LiOH can be produced using only electrochemical cells.

[0212] List of reference numerals:

[0213] 0 Electrochemical Cell

[0214] 1 First compartment

[0215] 2 Second compartment

[0216] 3 membrane

[0217] 4 Anode

[0218] 5 cathode

[0219] 6 First electrical lead

[0220] 7 Voltage Source

[0221] 8 Second electrical lead

[0222] 9 Unspecified

[0223] 10 Feed

[0224] 11 Unspecified

[0225] 12 Lean working medium

[0226] 13 Rich working medium

[0227] 14 Wastewater

[0228] 15 Target product

[0229] 16 Separation equipment

[0230] H2O water

[0231] H2 Hydrogen

[0232] O2 oxygen

[0233] LiOH lithium hydroxide

[0234] OH - OH anion

[0235] Li + Lithium cation

[0236] U Voltage

[0237] I Current

[0238] A Effective area

[0239] C F LiOH concentration in feed

[0240] C W LiOH concentration in wastewater

[0241] C M0 LiOH concentration in lean working medium

[0242] C M1 LiOH concentration in rich working medium

Claims

1. A method for producing hydrogen and lithium hydroxide, comprising the following steps: a) providing a feed comprising at least water, Li ions and impurities, wherein the concentration of Li ions in the feed is C F 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 of lithium hydroxide in the lean working medium is C based on the total weight of the lean working medium. M0 At least 50 ppm by weight; c) providing at least one electrochemical cell, wherein the electrochemical cell has the following characteristics: 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 disposed; iii. The electrochemical cell comprises a membrane separating the first compartment from the second compartment, the membrane having an area A; iv. The membrane comprises an inorganic material having Li ion conductivity and being 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) filling the first compartment with the feed; f) filling the second compartment with the lean working medium; g) charging the electrochemical cell with a voltage U taken from the 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 between 100 A / m 2 and 500A / m 2 Between or 150A / m 2 and 350A / m 2 between; h) taking out wastewater containing at least water, Li salt dissolved therein, oxygen and impurities from the first compartment, wherein the concentration of Li ions in the wastewater is C based on the total weight of the wastewater. W is lower than the concentration C of Li ions in the feed based on the total weight of the feed. F ; i) taking out a rich working medium comprising water, hydrogen and lithium hydroxide from the second compartment, wherein the concentration C of lithium hydroxide in the rich working medium is based on the total weight of the rich working medium. M1 greater than the concentration C of lithium hydroxide in the lean working medium based on the total weight of the lean working medium M0 , and wherein the concentration of lithium hydroxide in the rich working medium is C based on the total weight of the rich working medium. M1 Greater than at temperature T M1 The solubility of lithium hydroxide in water at a temperature T M1 refers to the temperature of the rich working medium when it is taken out from the second compartment.

2. The method according to claim 1, characterized in that: The rich working medium contains solid lithium hydroxide when it is withdrawn from the second compartment.

3. The method according to claim 1 or 2, characterized in that: The temperature T of the rich working medium when it is taken out from the second compartment M1 Between 20°C and 60°C.

4. The method according to claim 3, characterized in that Based on the total weight of the rich working medium, the concentration of lithium hydroxide in the rich working medium is C M1 More than 0.1276 kg / kg or more than 0.138 kg / kg or more than 0.146 kg / kg, in each case calculated as LiOH; or Based on the total weight of the rich working medium, the concentration of lithium hydroxide in the rich working medium is C M1 Greater than 0.21 kg / kg or greater than 0.231 kg / kg, calculated in each case as LiOH.H2O.

5. The method according to any one of claims 1 to 4, characterized in that Based on the total weight of the lean working medium, the concentration of lithium hydroxide in the lean working medium is C M0 Less than 12.8% by weight.

6. The method according to any one of claims 1 to 4, characterized in that The feed contains anions selected from sulfate, carbonate, hydroxide and chloride.

7. The method according to any one of claims 1 to 6, 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. A method according to any one of the preceding claims, wherein the conductivity of the inorganic material present in the membrane to Li ions, measured by the "impedance spectroscopy" method described herein, 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 not more than 100×10 -5 S / m.

9. The method according to claim 8, characterized in that The inorganic material is a compound with the following stoichiometry (LATP): Li 1+x Al x Ti 2-x (PO4)3 Wherein: 0.1≤x≤0.3, wherein preferably x=0.

3.

10. The method according to claim 8, characterized in that The inorganic material is a compound with the following stoichiometry (LATSP): There 1+x+y To the x You 2-x Yes y P 3-y OR 12 Among them: 0.1≤x≤0.3 and 0.2≤y≤0.

4.

11. The method according to claim 8, characterized in that The inorganic material is a compound with the following stoichiometry (LAGTSP): The 1+x+y Al x Ti 2-x If y P 3-y O 12 *nGeO2 Among them: 0≤x≤1 and 0≤y≤1 and 0≤n≤1.

12. The method according to claim 8, characterized in that The inorganic material is a compound with the following stoichiometry (LAGTP): Li 1.4 Al 0.4 (Ge 1-x Ti x ) 1.6 (PO4)3 Among them: 0≤x≤1.

13. The method according to claim 8, characterized in that The inorganic material is a compound (LAGP) having the following stoichiometry: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> 1+x <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> Ge<h2 style=";text-align:left;direction:ltr"> 2-x <h2 style=";text-align:left;direction:ltr"> (PO4)3 Where: x=0 or x=0.2 or x=0.

4.

14. The method according to claim 8, characterized in that The inorganic material is a compound having the following stoichiometry (LLTO): He 3x The (2 / 3)-x□(1 / 3)-2x TiO3 Where: 0≤x≤0.

16.

15. The method according to any one of the preceding claims, comprising the steps of: k) providing separation equipment; 1) Separating lithium hydroxide from the rich working medium by means of the separation device.

16. The method according to claim 15, characterized in that In the following step 1), lithium hydroxide is separated from the rich working medium by means of the separation device to obtain a product having the following composition: Parts by weight herein add up to 100% and are based on the total weight of the product.

17. The method according to claim 15 or 16, characterized in that The step 1) separates lithium hydroxide from the rich working medium by means of a separation device; The lean working medium is obtained so that the step b) providing a lean working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration of lithium hydroxide in the lean working medium is C based on the total weight of the lean working medium. M0 At least 50 ppm by weight; This is carried out with the aid of the separation device.

18. The method according to claim 15, 16 or 17, characterized in that: The electrochemical cell and the separation device are arranged at the same location.

19. The method according to claim 18, characterized in that At least the following method steps are performed continuously i) removing a rich working medium comprising water, hydrogen and lithium hydroxide from the second compartment; and 1) Separating lithium hydroxide from the rich working medium by means of the separation device.

20. The method according to any one of claims 15 to 19, characterized in that The separation device is a solid separator.

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

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