Production of hydrogen and lithium hydroxide in basic environments

Abstract

LiSiCon membranes can be economically operated on an industrial scale. + To identify a process for the electrochemical production of LiOH from contained water, in particular, a process that has good energy efficiency and achieves high membrane life, even when the feed used contains impurities that are harmful to the LiSICon material. A process for producing hydrogen and lithium hydroxide, comprising: a) providing a feed containing at least water, Li cations, anions, and also impurities, wherein the concentration of Li cations in the feed, C F is at least 200 ppm (by weight) or between 500 ppm (by weight) and 140,000 ppm (by weight) in each case based on the total weight of the feed, and the pH of the feed is between 2 and 9 as measured using a glass electrode at 25°C; b) providing a lean working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration C of lithium hydroxide in said lean working medium is M0 is at least 50 ppm (by weight) based on the total weight of said lean working medium; c) providing a basic compound; d) providing at least one electrochemical cell, the electrochemical cell having the following characteristics: i. the electrochemical cell includes a first compartment having an anode disposed therein; ii. the electrochemical cell includes a second compartment having a cathode disposed therein; iii. the electrochemical cell includes a membrane separating a first membrane from a second membrane, the membrane having an area A; iv. the membrane comprises an inorganic material that is conductive to Li ions and electrically insulating; e) providing at least one voltage source connected to said anode via a first electrical lead and connected to said cathode via a second electrical lead; f) metering the basic compound into the feed to obtain an intermediate, the pH of which is between 9 and 13 as measured at 25°C using a glass electrode; g) filling the first compartment with the intermediate; h) filling the second compartment with the lean working medium; i) charging the electrochemical cell with a voltage U drawn from the voltage source so that a current I flows between the anode and the cathode, wherein the ratio Q of the current intensity of the current I to the area A of the membrane is 100 A / m 2 ~500A / m 2 or 150A / m 2 ~350A / m 2 the charging step; j) withdrawing wastewater from the first compartment, the wastewater containing at least water, dissolved Li salts therein, oxygen, and also impurities, wherein the concentration of Li ions in the wastewater, C W is the concentration of Li ions in the feed, C, based on the total weight of the wastewater. F Lower than, pull out step; k) withdrawing a rich working medium containing water and lithium hydroxide and also hydrogen from the second compartment, wherein the concentration C of lithium hydroxide in the rich working medium is M1 is the concentration C of lithium hydroxide in the lean working medium based on the total weight of the rich working medium M0 A process that includes a step of drawing out, which is higher than the above.

Description

[Technical Field]

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

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

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

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

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

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

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

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

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

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

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

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

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

[0014] US Pat. No. 9,222,148 also discloses the separation of lithium hydroxide by membrane electrolysis on a LiSICon membrane and the resulting precipitation of lithium hydroxide hydrate.

[0015] In addition to the use of ceramic LiSICon membranes, electrolytic processes for the separation of lithium operating with organic ion exchange membranes have also been disclosed.

[0016] For example, EP 3805428 A1 describes the electrolytic production of lithium hydroxide. Similar to electrolysis, the electrochemical conversion of lithium to lithium hydroxide is operated. To obtain the necessary reactants, water undergoes simultaneous electrochemical splitting. This is carried out using a bipolar three-compartment cell equipped with ion-exchange membranes. Commercially available ion-exchange membranes are used: Asahi® AVV, Nafion® 902, Fumatech® FAB, Fumatech® FKB, and Neosepta® CMB. The chemical nature of these ion-exchange membranes is not disclosed in EP 3805428 A1, but they are likely organic membrane materials. The three-compartment cell operates in an acidic medium. The feed uses water containing Li salts, particularly lithium sulfate (LiSO4) or lithium chloride (LiCl).

[0017] A two-stage electrodialysis / electrolysis production of lithium hydroxide from aqueous lithium sulfate and / or lithium bisulfate with simultaneous water splitting is disclosed in U.S. Pat. No. 10,036,094. The first stage uses an electrochemical cell with two compartments, and the second stage uses a three-compartment cell. The prevailing pH in the three-compartment cell can be between 8 and 10. The cell is equipped with an ion-exchange membrane. The chemical composition of the ion-exchange membrane is not given. The following commercially available membranes are mentioned: Fumatech® FAB, Astom® ACM, Asahi® MV, Nafion® 324, and Astom® AHA. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] US Patent Application Publication No. 2016 / 0201163 [Patent Document 2] International Publication No. 2019055730 [Patent Document 3] U.S. Patent No. 9,222,148 [Patent Document 4] European Patent Application Publication No. 3805428 [Patent Document 5] U.S. Patent No. 10036094

Non-licensed literature

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[0020] A fundamental drawback of polymeric membranes is their permeability to water, which leads to dilution of the anolyte with water from the catholyte. Furthermore, organic ion exchange membranes have lower ion selectivity than inorganic LiSICon materials. They are + Not only Na + As well as the purity of the target product, the electrical efficiency of the process is also reduced: if electrolysis is carried out using a non-ion selective membrane, the unwanted Na + The transport of Na to the second compartment also consumes valuable electrical energy. + is converted to undesired by-products by unintended electrochemical processes, reducing the energy efficiency of the process based on the yield of the target product, Li. Finally, these films are 2+ and Ca 2+ Over time, these cations poison the membrane, thereby limiting the useful life of organic ion exchange membranes.

[0021] Glass-ceramic LiSICon materials promise better ion selectivity. However, the stability of LiSICon membranes against impurities remains a critical issue for industrial implementation. For example, Li ions generated in the reprocessing of spent LIBs are also present. + The contained water is especially Na + and K. + These cations appear to occupy defects in the crystal structure, thereby allowing Li ions to pass through the membrane. + This virtually stops cation transport. The useful life of the electrochemical cell then expires. The high cost of LiSICon materials means that recycling Li from LIBs is uneconomical if the membrane has a short useful life. Furthermore, brine from Li-salt lakes has a naturally high sodium content, making it impossible to contact known LiSICon membranes. Therefore, lithium from the lakes must be dissolved and then recrystallized via a stepwise process that requires energy-intensive thermal separation and / or large amounts of water. While water can be evaporated here by solar radiation, water to dissolve LiCl is scarce in the South American desert. Therefore, this route is highly problematic there.

[0022] Another practical problem is the high specific electrical resistivity of LiSICon materials. This results in electrochemical cells with high ohmic internal resistance, which means that the process has correspondingly high electrical energy requirements. To reduce this, the membrane could theoretically be made thinner. However, a thinner material would have a shorter lifetime in aggressive environments.

[0023] Based on all the above, the problem addressed by the present invention is to produce LiSiCon films using LiSiCon membranes that can be operated economically even on an industrial scale. + The objective of this study is to identify a process for the electrochemical production of LiOH from water. In particular, the process must have good energy efficiency and achieve high membrane life, even when the feed used contains impurities that are harmful to the LiSICon material. [Means for solving the problem]

[0024] This problem is solved by the process according to claim 1.

[0025] Accordingly, the present invention first provides a process for producing hydrogen and lithium hydroxide, comprising: a) providing a feed containing at least water, Li cations, anions, and also impurities, wherein the concentration of Li cations in the feed, C F is at least 200 ppm (by weight) or between 500 ppm (by weight) and 140,000 ppm (by weight) in each case based on the total weight of the feed, and the pH of the feed is between 2 and 9 as measured using a glass electrode at 25°C; b) providing a lean working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration C of lithium hydroxide in the lean working medium is M0 is at least 50 ppm (by weight) based on the total weight of the lean working medium; c) providing a basic compound; d) providing at least one electrochemical cell, the electrochemical cell having the following characteristics: i. the electrochemical cell includes a first compartment having an anode disposed therein; ii. the electrochemical cell includes a second compartment having a cathode disposed therein; iii. the electrochemical cell includes a membrane separating a first membrane from a second membrane, the membrane having an area A; iv. the membrane comprises an inorganic material that is conductive to Li ions and electrically insulating; e) providing at least one voltage source connected to the anode via a first electrical lead and connected to the cathode via a second electrical lead; f) metering a basic compound into the feed to obtain an intermediate, the pH of which is between 9 and 13 as measured at 25°C using a glass electrode; g) filling the first compartment with an intermediate; h) filling the second compartment with a lean working medium; i) charging the electrochemical cell with a voltage U drawn from a voltage source so that a current I flows between the anode and the cathode, the ratio Q of the current intensity of the current I to the area A of the membrane being 100 A / m 2 ~500A / m 2 or 150A / m 2 ~350A / m 2 the charging step; j) withdrawing wastewater from the first compartment, the wastewater containing at least water, dissolved Li salts therein, oxygen, and also impurities, wherein the concentration of Li ions in the wastewater, C W is the concentration of Li ions in the feed, C, based on the total weight of the wastewater. F Lower than, pull out step; k) withdrawing a rich working medium containing water and lithium hydroxide and also hydrogen from the second compartment, wherein the concentration C of lithium hydroxide in the rich working medium is M1 is the concentration C of lithium hydroxide in the lean working medium, based on the total weight of the rich working medium. M0 The present invention provides a process including a step of extracting a higher value than the above. [Brief explanation of the drawings]

[0026] [Figure 1] The functional principle of simultaneous Li+ membrane electrolysis and water electrolysis in an electrochemical cell using a LiSICon membrane is presented. [Figure 2] 1 illustrates the functional principle of recirculation between the electrochemical cell and the separation device. [Figure 3] 1 is a graph showing the results of Example 1. [Figure 4] 1 is a graph showing the results of Example 2. [Figure 5] 1 is a graph showing the results of Example 3. [Figure 6] 1 is a graph showing the results of Example 4. [Figure 7] 1 is a graph showing the results of Example 5. [Figure 8] 1 is a graph showing the results of Example 6. [Figure 9] 1 is a graph showing the results of Example 7. [Figure 10] 10 is a graph showing the results of Example 9. [Figure 11] 1 is a graph showing the results of Example 10. [Figure 12] 1 is a graph showing the results of Example 10. [Figure 13] 1 is a graph showing the results of Example 11. [Figure 14] 1 is a graph showing the results of Example 11. [Figure 15] 1 is a graph showing the results of Example 12. [Figure 16] 1 is a graph showing the results of Example 12. DETAILED DESCRIPTION OF THE INVENTION

[0027] A particular aspect of the process according to the invention is that the selective separation of lithium by the membrane and the electrolysis of water occur simultaneously within the cell. In water electrolysis, water (H2O) is electrochemically split into H2 and O2. At the cathode, OH - However, OH - Anions cannot pass through the LiSICon membrane and reach the cathode compartment. + At the anode, oxygen and H + is formed.

[0028] Thus, the simultaneous operation of Li+ membrane separation and water electrolysis in an electrochemical cell using a LiSICon membrane results in the direct formation of lithium hydroxide (LiOH) and molecular hydrogen (H2). While some LiOH dissolves in water and H2, most of it is discharged in gas form. Water containing LiOH and dissolved gaseous H2 is extracted from the cathode compartment. The LiOH is separated from the water. This allows for the selective migration of lithium ions through the membrane to extract LiOH of sufficient purity for use in battery production.

[0029] The co-produced hydrogen can be collected and used in the hydrogen economy. If the electrochemical cell is operated with green electricity, the process also has a small CO2 footprint.

[0030] The feed required for combined Li separation and water electrolysis is Li + This water contains cations. Such water can be produced during the reprocessing of spent LIBs, or Li brines from natural deposits can be used.

[0031] An important aspect of the process according to the invention is that the electrochemical process is carried out in a basic medium, more precisely at a pH of 9-13. This allows efficient water electrolysis, which is a prerequisite for the direct production of LiOH. Furthermore, preliminary long-term studies have shown that the LiSICon material has a particularly long lifetime in this pH range, even at high current densities.

[0032] The prevailing pH is preferably between 9 and 13 in both the first and second compartments. The pH in the two cells can be the same or different, as long as it is between 9 and 13 in both cases. This is because studies of water splitting half-cell reactions have shown that a combination of an anolyte cell operating on an acidic feed and a catholyte cell operating on a basic working medium requires a higher water splitting voltage than a combination of two half-cells, each with a basic feed. Therefore, a basic pH in both half-cells (compartments) is particularly advantageous, since it requires a lower voltage for the same process. The energy savings resulting from the voltage reduction when a basic process exists in both compartments, compared to a process in which an acidic pH exists in the anode compartment and a basic pH prevails in the cathode compartment, are approximately in the range of 5% to 15%, depending on the voltage level selected for the membrane process.

[0033] Because lithium-containing material streams from battery recycle or seawater are typically not basic but instead tend to be acidic (pH 4-9), in accordance with the present invention, the pH is adjusted by adding a basic compound to the feed. Only the resulting intermediate with the desired pH of 9-13 is fed to the cell. pH values ​​are specified for a temperature of 25°C. pH is measured using a glass electrode calibrated with a commercially available test solution.

[0034] The cathode compartment is filled with a working medium, which is water with various concentrations of LiOH. At the inlet to the second compartment, the LiOH concentration c M0 is at least 50 ppm (by weight). In the spill, the LiOH concentration c M1 is much higher. Therefore, the inflow is called the "lean working medium" and the outflow is called the "rich working medium." The attributes "lean" and "rich" refer to the LiOH content. M0The lower limit of the LiOH content in the lean working medium of >50 ppm (by weight) must be met to allow the process to start at a low electrical resistance in the working medium: it was found that if water containing no LiOH was charged to the second compartment, the desired production of LiOH and H2 did not proceed very well. There is no specific upper limit for the LiOH concentration in the lean working medium. However, otherwise the process would not produce LiOH, so c M0 <c M1 50 ppm by weight of LiOH is equivalent to 15 ppm by weight of lithium.

[0035] A further important aspect of the process according to the invention is the high current density at which it is operated. In particular, the current density, i.e. the ratio Q of the current intensity I to the membrane area A, is 100 A / m 2 ~500A / m 2 or preferably between 150A / m 2 ~350A / m 2 These high current densities allow for high electrical efficiency, but also require the membrane material to exhibit good stability under harsh conditions. Therefore, the membrane material selected is an inorganic material that is electrically insulating and simultaneously conductive to Li ions. An example of a suitable membrane material is the glass-ceramic LiSICon.

[0036] The basic compound used to adjust the pH of the intermediate is preferably one of the following substances or mixtures: calcium hydroxide (Ca(OH)2), potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH) and ammonium hydroxide (NH4OH). These substances are preferably used in the form of aqueous solutions, in other words potassium hydroxide solution, sodium hydroxide solution, lithium hydroxide solution or aqueous ammonia. Such aqueous solutions are easy to meter. Potassium hydroxide solution and sodium hydroxide solution are relatively inexpensive. The lithium hydroxide solution is preferably produced in the process itself.

[0037] It is very particularly preferred to use Ca(OH)2 as the basic compound. Calcium hydroxide is used in particular in its hydrated form, i.e. as slaked lime. Slaked lime is easily obtainable. The advantage of slaked lime over potassium hydroxide and sodium hydroxide solutions is that it contains virtually no K or Na. This is because the intermediate is the membrane poison K. + and Na + This means that the water will no longer be contaminated by

[0038] The basic compound is optimally metered into the feed so that the intermediate pH, measured using a glass electrode at 25°C, is between 9 and 12. In this pH range, water splitting works very well and the membrane is not attacked. The glass electrode for determining pH should be calibrated in the standard manner using the specified test solution.

[0039] The electrochemical cell can be operated at temperatures other than 25°C. The pH should not be adjusted: the intermediate should have a pH at the cell temperature equivalent to a pH of 9-12 at 25°C. The cell temperature may be between 20°C and 70°C.

[0040] The addition of a basic compound has the added benefit of binding undesirable ions present in the feed, thereby protecting the membrane and improving product purity. More specifically, the addition of a basic compound makes it possible to work with feeds containing one or more of the following anions: sulfate, carbonate, hydroxide, chloride, and fluoride.

[0041] This setup allows anions to exist in equilibrium with the corresponding protonated ions in aqueous solution. The exact concentrations now depend on the exact pH of the respective solutions and can be calculated using the corresponding acid and base constants. The calculation is shown below: Ruland(ed.) et al.:Analytik:Daten,Formeln,Ubungsaufgaben[Analytics:data,formulae,exercises],edition 109,2019,Walter de Gruyter GmbH&Co.KG pages 257ff. In addition to the anions mentioned, the feed may also contain impurities in the form of compounds of the following elements: B, Na, Mg, Al, Si, K, Ca, Mn, Fe, Co, Ni, Cu, and C. The listed alkali and alkaline earth metals are elements found together with lithium in natural deposits, 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. The carbon originates from organic compounds present in the LIBs, such as films, separators, sealants, or adhesives. According to the present invention, a membrane containing inorganic materials is used. Therefore, the required ion selectivity is achieved differently than with polymeric membranes. The membrane is preferably composed entirely of inorganic materials. Composite membranes containing inorganic materials only as a coating on a support material or in which inorganic materials are dispersed in different types of matrix materials have proven to be erroneous approaches.

[0042] For the process to work, the inorganic material must conduct Li ions and simultaneously act as an electrical insulator.

[0043] The specific conductivity σ of Li-ions is at least 1*10 at a temperature of 23°C. -5 S / m or at least 5*10 -5 S / m or at least 10*10 -5 S / m and 100*10 -5 The Li conductivity of the material is measured by impedance spectroscopy. This measurement is performed as follows: The measurement setup comprises two cylindrical electrodes between which the sample is placed. A weight is placed on the sample to ensure optimal contact with the electrodes and a reproducible contact pressure.

[0044] A potentiostat (Zahner-Elektrik I. Zahner-Schiller GmbH & Co. KG, Kronach-Gundelsdorf, Germany) is connected to the electrodes and controlled via Thales software (Zahner). Measurements are performed in the frequency range of 1 Hz to 4 MHz and at an amplitude of 5 mV using samples polished and sputtered onto a thin conductive gold layer.

[0045] The measurement results are presented in the form of a Nyquist plot and evaluated using analytical software (Zahner). The electrical resistance is read at the maximum value of the Nyquist plot curve. The specific ionic conductivity σ [mS / cm] is then calculated using the formula σ = (h 10 4 ) / (R π / 4 d 2 ) where h is the height of the sample (mm), R is the measured electrical resistance (Ω), and d is the diameter of the sample (mm).

[0046] The specific conductivity of electrons (electrical conductivity) is 10 -7 Less than S / cm (10 -9 S / m), or 10 -12 Less than S / m or 10 -16 S / m. Therefore, from the viewpoint of electronic conduction, inorganic materials are classified as non-conductors.

[0047] It is preferred to use LiSICon as the inorganic material. LiSICon material is a glass-ceramic material that conducts lithium ions and simultaneously acts as an electrical insulator. In principle, all known LiSICon materials can be used as inorganic materials for the purposes of the present invention. Known LiSICon materials meet the above-specified requirements for both the electrical conductivity and ionic conductivity of inorganic materials.

[0048] For example, the LiSICon material lithium aluminum titanium phosphate (LATP) can be used. Thus, in one variant of the invention, the inorganic material is a compound of the following stoichiometry:

[0049] [ka] [wherein 0.1≦x≦0.3, preferably x=0.3].

[0050] Alternatively, the LiSICon material lithium aluminum germanium phosphate (LAGP) can be used. Thus, in one variant of the invention, the inorganic material is a compound of the following stoichiometry:

[0051] [ka] [wherein x=0 or x=0.2 or x=0.4].

[0052] Alternatively, the LiSICon material lithium aluminum titanium silicon phosphate (LATSP) can be used. Thus, in one variant of the invention, the inorganic material is a compound of the following stoichiometry:

[0053] [ka] [wherein 0.1≦x≦0.3 and 0.2≦y≦0.4].

[0054] As an alternative to the phosphates mentioned, the oxide LiSICon material lithium lanthanum titanium oxide (LLTO) can be used. Thus, in one variant of the invention, the inorganic material is a compound of the following stoichiometry:

[0055] [ka] [wherein 0≦x≦0.16].

[0056] However, it is particularly preferred to use LiSICon, which is derived from lithium aluminum germanium phosphate but also contains titanium, and is called LAGTP.

[0057] Thus, in a preferred variant of the invention, the inorganic material is a compound of the following stoichiometry:

[0058] [ka] [wherein 0≦x≦1].

[0059] In a particularly preferred development of the invention, LATSPs are used which additionally contain germanium, and are referred to as LAGTSPs.

[0060] Thus, in a particularly preferred variant of the invention, the inorganic material is a compound of the following stoichiometry:

[0061] [ka] [Wherein, 0≦x≦1, 0≦y≦1, and 0≦n≦1] LAGTSP is available, for example, from OHARA GmbH, Hofheim, Germany, available under the product name LICGC® AG01.

[0062] The lithium hydroxide is present in the rich working medium and is withdrawn from the second compartment together with it. To be able to utilize it, it must be separated from the rich working medium. For this purpose, a separation device is provided. Therefore, a preferred development of the invention comprises the following additional process steps: m) providing a separation device; n) Separating the lithium hydroxide from the rich working medium using a separator.

[0063] After the lithium hydroxide is separated from the rich working medium, the working medium can be disposed of as wastewater or, preferably, reused as lean working medium. For this, the LiOH is not completely separated, but instead a specific minimum concentration of 50 ppm LiOH is used. m0The separation apparatus must be operated so that the working medium is maintained above 0.05%. This allows the working medium to be recycled to the second compartment as lean working medium. This allows the working medium to be recirculated between the second compartment and the separation apparatus.

[0064] A preferred development of the invention therefore comprises the following additional process steps: n) separating the lithium hydroxide from the rich working medium using a separator to provide a lean working medium; Including, b) providing a lean working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration C of lithium hydroxide in the lean working medium is M0 is at least 50 ppm (by weight) based on the total weight of the lean working medium, This is done using a separation device.

[0065] To allow for the recirculation of the working medium between the separator and the second compartment, it makes sense to install both devices in the same location. This should be understood to mean an integrated production facility. The electrochemical cell and the separator are therefore part of an integrated facility.

[0066] It is also conceivable that the separation device could be located at a different location from the electrochemical cell, but in that case the working medium would have to be transported between the cell and the separation device, which makes little sense from an energy point of view.

[0067] At least the electrochemical cell is preferably operated continuously. This means that there is a constant flow between the two compartments. The first compartment has a continuous flow of intermediates, resulting in the production of wastewater, while the second compartment has a flow of working medium, which enters as lean working medium and exits as rich working medium. This allows for both higher throughput and continuous removal of membrane-damaging components of the intermediates and working medium. Therefore, continuous operation is expected to achieve better membrane stability than batch operation.

[0068] A key aspect of the present process is the simultaneous production of hydrogen and lithium hydroxide, which is made possible by the combined membrane electrolysis of Li+ and electrochemical water splitting in a basic medium.

[0069] In the simplest case, the voltage applied to an electrochemical cell is constant over time (DC voltage). However, it has been found to be advantageous to vary the voltage periodically over time. This results in an improvement in the membrane's service life. One explanation for this could be that membrane-damaging ions are washed out of the membrane during the periods when the cell is switched off.

[0070] In a preferred development of the process, the voltage drawn from the voltage source is varied periodically over time.

[0071] Preferably, the voltage varies in a waveform, which here may be a sine, square, triangular or sawtooth waveform.

[0072] In the simplest case, the waveform is obtained by periodically changing the polarity of a voltage (AC voltage).

[0073] However, more preferably, the voltage is varied by periodically switching it on and off. When the voltage is on, it remains constant. This results in a square wave. In this case, it can also be said that voltage pulsation occurs. It has been found to be advantageous if the period during which the voltage is switched on is longer than the period during which the voltage is switched off. Preferably, the period during which the switch is on is 3 to 7 times longer than the period during which the switch is off, preferably about 5 times longer.

[0074] Therefore, in a preferred development of the process, the waveform is square, i.e. it is formed from a first wave section, in which the voltage is switched on with a constant value, and a second wave section, following the first wave section, in which the voltage is switched off, the length of the first wave section being λ1 and the length of the second wave section being λ2, and the following relationship is satisfied:

[0075]

number

[0076] It should also be noted that with regard to the periodic variation of the voltage, the voltage does not necessarily have to change polarity as in an AC voltage. It is conceivable to make the voltage oscillate with an amplitude of approximately U=0, but it is preferable to not change the polarity (i.e., sign) of the voltage, but only the magnitude of the voltage. Therefore, in a preferred development of the process, the polarity of the voltage is maintained.

[0077] The invention will now be described in detail with reference to a process flow diagram, in which: Figure 1 shows the simultaneous Li+ / Li ... + The functional principles of membrane electrolysis and water electrolysis are shown.

[0078] FIG. 2 shows the functional principle of the recirculation between the electrochemical cell and the separation device.

[0079] The electrochemical cell 0 required to carry out the process is shown in Figure 1. It comprises a first compartment 1 and a second compartment 2. The two compartments 1 and 2 are separated from each other by a membrane 3. An anode 4 is located in the first compartment 1. A cathode 5 is located in the second compartment 2. Thus, the first compartment 1 can be referred to as the anode compartment, and the second compartment 2 can be referred to as the cathode compartment.

[0080] A first electrical lead 6 connects the anode 4 to a voltage source 7. A second electrical lead 8 connects the cathode 5 to the voltage source 7. The selected polarity of the voltage source 7 is such that the positive terminal of the voltage source 7 is connected to the anode 4 and the negative terminal of the voltage source 7 is connected to the cathode 5. This polarity is always maintained even though the magnitude of the voltage U drawn from the voltage source 7 varies over time. However, in the simplest case, U is constant over time.

[0081] An electric current I flows through two electrical leads 6 and 8 via a voltage source 7. There is no electrical short circuit between the two electrodes 4 and 5 through the membrane 3, as the membrane 3 acts as an electrical insulator.

[0082] The membrane 3 is a flat sheet membrane made entirely of LiSICon material. The anode 4 is a flat metal plate made of titanium, niobium, or tantalum. The cathode 5 is also a flat metal plate made of titanium or nickel. In the simplest case, a stainless steel plate is used as the cathode. The anode 4, cathode 5, and membrane 3 all have the same shape and can be rectangular or circular. This is not clear from the side view in Figure 1. Instead of metal plates, it is also possible to use expanded metal, mesh, or netting of a certain material as electrodes.

[0083] The electrochemical cell 0 has an active area A corresponding to the surface area of ​​the membrane 3 , the anode 4 and the cathode 5 .

[0084] During operation, the first compartment 1 is filled with an intermediate 9. The intermediate 9 is an aqueous solution containing Li+ ions. From an electrochemical point of view, the intermediate 9 is considered an anolyte.

[0085] Intermediate 9 is obtained by mixing feed 10 with basic compound 11. Feed 10 may be a Li leachate from a natural deposit or a material stream resulting from the reprocessing of spent LIBs. The concentration of Li+ cations in feed 10 (formula symbol c F) should be at least 200 ppm (by weight) based on the total mass of the feed. Seawater has a low Li concentration and must first be concentrated before use in the process. Feed 10 also contains anions such as sulfate or chloride. Feed 10 also contains impurities. The anions and impurities are not shown in Figure 1. The main component of feed 10 is water, HO. The pH of the feed is between 2 and 9.

[0086] The basic compound 11 is optimally calcium hydroxide Ca(OH)2 (slaked lime). The metering of the basic compound 11 into the feed 10 results in the formation of the intermediate 9. The purpose of adding the basic compound 11 to the feed 10 is to raise the pH to the alkaline range, more precisely to a pH between 9 and 13. The electrochemical process in the cell is carried out in a basic medium, according to the invention. The dosage of the basic compound 11 is therefore selected so as to achieve a pH between 9 and 13 in the intermediate. The intermediate 9 is fed into the first compartment 1.

[0087] The second compartment is filled with lean working media 12. The lean working media 12 is Li + Cation concentration C M0 The concentration of water is low. M0 is at least 50 ppm (by weight) based on the total mass of the lean working medium 12. From an electrochemical standpoint, the lean working medium 12 is considered to be the catholyte.

[0088] The electrochemical cell 0 is also charged with a voltage U drawn from a voltage source 7. This has the following effects:

[0089] First, water electrolysis occurs, where water (H2O) is electrochemically split into hydrogen (H2) and oxygen (O2). At the cathode 5, OH - However, OH - The anions cannot pass through the membrane 3 and are transported to the cathode compartment 2 via the Li + At the anode 4, oxygen and H +is formed.

[0090] The formation of LiOH in the cathode compartment 2 is sustained by the migration of Li cations from the intermediate 9 to the cathode 5, driven by the voltage U. They cross the membrane 3 due to the membrane's Li conductivity and accumulate in the working medium (membrane electrolysis). This forms the rich working medium 13, which is withdrawn from the second compartment 2. The Li ion concentration in the rich working medium 13 is higher than in the lean working medium 12, so c M1 >c M0 is.

[0091] Therefore, in electrochemical cell 0, water electrolysis, Li + The membrane electrolysis and synthesis of LiOH proceed simultaneously.

[0092] Thus, the simultaneous operation of Li+ membrane electrolysis and water electrolysis in an electrochemical cell results in the direct formation of lithium hydroxide (LiOH) and molecular hydrogen (H2). LiOH dissolves in water, and hydrogen is partially dissolved in water and also exists in gaseous form. Water containing LiOH and dissolved hydrogen is withdrawn from the cathode compartment of the cell as the rich working medium 13. Similarly, gaseous hydrogen is withdrawn from the second compartment 2.

[0093] As a result of membrane electrolysis, intermediate 9 becomes depleted of Li+, producing wastewater 14. W <c F Here, the formula symbol c W represents the Li ion concentration in the wastewater 14 based on the total mass of the wastewater 14. F represents the concentration of Li ions in the feed 10 based on the total mass of the feed 10.

[0094] FIG. 2 shows how LiOH is extracted as the target product 15 from the rich working medium 13.

[0095] For this purpose, a separation device 16 is provided to which the rich working medium 13 is conveyed. The separation device 16 separates the target product 15, which has a particularly high concentration of LiOH, from the rich working medium 13. The target product also contains water and impurities, depending on the desired specifications of the target product.

[0096] Separator 16 can be a distillation column or a crystallizer.

[0097] The LiOH-depleted effluent stream from the separator 16 is recycled to the second compartment 2 of the electrochemical cell 0 as lean working medium 12 .

[0098] As mentioned above, the poor working medium 12 is required to have a specific LiOH concentration C so that the process in the electrochemical cell 0 can be initiated in the desired manner due to the low initial resistance. M0 It is necessary to have a concentration c M0 The desired concentration C must be at least 50 ppm (by weight) based on the total mass of the lean working medium 12. M0 To ensure this, the separator 16 operates such that not all of the LiOH is separated from the rich working medium 13.

[0099] In addition to lithium hydroxide LiOH, the process also produces H2, which is at least partially dissolved in the rich working medium 13 and is withdrawn together with LiOH from the second compartment 2. Some of the hydrogen escapes from the second compartment 2 in gaseous form.

[0100] Since hydrogen H2 is easily degassed from water, it does not require much effort to remove it from the working medium. Only when hydrogen H2 is utilized as the second target product, a corresponding second separation device is provided (not shown) from which hydrogen can be obtained separately with suitable quality / purity.

[0101] The water HO present in the rich working medium 13 is recycled as completely as possible as lean working medium 12. Only the water present in the target product 15 is lost from the process; this must be replenished to the lean working medium 12 as needed (not shown). The water in the intermediate 9 originating from the feed is not finally recycled between the second compartment 2 and the separation device 16 because the membrane 3 is impermeable to water. [Example]

[0102] Experimental setup and procedure The following discussion aims to explain the effect of impurities in the form of foreign ions on ceramic lithium conducting membranes during electrolysis. The effects of pH and voltage cycling are also described.

[0103] To carry out electrolysis, the electrolysis cell is first assembled and the anolyte and catholyte containers are connected, with care being taken to ensure that the inlet and outlet flows are connected on the same side in each case.

[0104] The anodes and cathodes used were in each case circular disks with a diameter of 19.5 mm and a thickness of 1 mm. The materials were in each case titanium expanded metal plates coated on both sides with IrTi mixed oxide (12 g Ir / m, 1 AF D 1.5 mm) from Metakem GmbH, 61250 Usingen, Germany.

[0105] The sampled membranes were also circular disks with a diameter of about 25 mm. The membrane thickness was about 1 mm. The material of the sampled membranes is specified in each example.

[0106] The electrolysis and corresponding storage vessels are blanketed with nitrogen throughout the process to prevent the formation of lithium carbonate. Each cell has a separate anolyte container and a separate catholyte container. Each container is filled with approximately 1 kg of liquid. The exact mass is determined by reweighing. In all experiments, the catholyte was always a 5 mmol / L LiOH solution (corresponding to 120 ppm LiOH by weight). The anolyte is in each case a lithium salt solution of various lithium salts at various concentrations.

[0107] The experiment begins when the pump is switched on and the desired voltage is applied. The maximum flow rate is 900 mL / min. Samples are collected every 30 minutes, or at longer intervals if agreed. The first 3 mL of sample collected is discarded. For each sample collected, the output is recorded in each case and the pH and conductivity of the sample are determined. The sample is then returned to a suitable container, keeping the volume substantially constant.

[0108] At the end of the experiment, the vessel is emptied and all leads and membranes are rinsed with demineralized water. The cell is disassembled, the membrane is photographed, and SEM images of the catholyte and anolyte sides are recorded to document any damage or changes to the membrane.

[0109] To confirm the hypothesis that low pH adversely affects membrane performance, several experiments were conducted involving adjustment of anolyte pH. Experiments without pH adjustment yielded very poor results. In experiments involving pH adjustment, the pH of the anolyte solution was adjusted to the desired range by appropriately dosing a basic compound before the experiment began. If this occurred during the experiment, additional base was metered in to maintain the pH. In contrast, there were experiments in which the pH decreased during electrolysis, consistent with the solution's natural behavior.

[0110] In experiments involving voltage pulsing, the voltage supply is interrupted at defined intervals so that no voltage is applied to the electrochemical cell during this time. Over time, the voltage operates in a square waveform with no change in polarity. The purpose of this is to allow potentially interfering ions (H) to dissipate during the voltage-free time. +), which reduces damage to the membrane and improves membrane performance.

[0111] Membrane performance is expressed as permeability (g Li*mm / m 2 *h) and permeance (g Li / m 2 *h). Permeance indicates how much mass of lithium is transported through the membrane per unit membrane area and unit time. Permeance also takes membrane thickness into account, and therefore makes it possible to compare different membrane types with different thicknesses. Very thin membranes can tolerate very high permeance, but if concentration polarization effects are present in the membrane cell, permeance gives an inaccurate picture, so both are necessary for a comprehensive description of performance. When membrane thickness is taken into account, transport is no longer limited by the membrane and therefore no longer serves a useful purpose.

[0112] All measurements shown in the examples are subject to a measurement error of approximately ±10% due to imprecision in positioning the electrodes relative to each other, in determining the thickness of the film sample, and in determining concentration by conductivity measurements.

[0113] All ceramics used originated from the manufacturers listed in Table 0 and can be ordered from these sources under the corresponding product designations.

[0114] [Table 0]

[0115] The lithium hydroxide used was analytical grade from Aldrich. All other materials used were of technical grade.

[0116] Unless otherwise stated, LATSP membranes (LICGC®, Ohara) with a thickness of approximately 1 mm were used. The membrane disks were 100x10 5 Pa~200*10 5They were produced by the SPS sintering process at a pressure of 100 Pa and a temperature of 950 °C or alternatively were obtained directly from various manufacturers (Ohara, Ampcera, Toshima) in sizes suitable for the measurement cell.

[0117] Sintering process description Sintering by FAST / SPS The LATSP powder used was sintered using FAST / SPS (Field-Assisted Sintering Technology / Spark Plasma Sintering). Sintering was performed with simultaneous pressure and temperature ramps to achieve high compaction and effective sintering in a very short sintering time. The sintering die assembly consisted of a graphite die with an outer diameter of 80 mm, an inner diameter of 36 mm, and a height of 55 mm, two graphite half-shells with 10 mm wall thicknesses and the same height, and two graphite punches with a diameter of 25 mm and a height of 30 mm. The half-shells were placed in the die, and one punch was introduced into the half-shells from below. Before weighing 2.5 g of powder onto the lower punch and inserting it into the die, a graphite foil was placed on the punch for better contact. After weighing the powder, a second graphite foil was placed on the powder, and the upper punch was introduced into the half-shells. The die assembly was placed in the furnace chamber of a FAST / SPS furnace between two plates, each made of carbon fiber-reinforced graphite. The assembly is contacted via the electrode path and the desired pressure is built up. The die is then heated by an alternating current, allowing it to reach high temperatures in a short time. The temperature is gradually increased to 250°C over 5 minutes, and then continued at a rate of 130°C / min until a maximum temperature of 900°C is reached and held for another 5 minutes. During the temperature increase, the pressure is also increased to 43 MPa over 5 minutes and held for another 5 minutes. At the end of the hold time, the upper electrode is released from contact with the die, allowing it to cool. The sintered film can then be removed from the mold.

[0118] Example 1 (LATSP) First, the voltage dependence of the ceramic membrane during electrolysis was investigated. Electrolysis was carried out using 0.1 mol / L LiOH and 1 mol / L LiOH at voltages of 3 V to 6 V. The measurement results are shown in Table 1.

[0119] A graphical plot of the values ​​reveals a linear relationship. The intersection of the line with the x-axis at approximately 2 V is derived from the water decomposition voltage and the internal resistance of the cell. This intersection is virtually identical for both concentrations. The plot is shown in Figure 3.

[0120] [Table 1]

[0121] Example 2 (LATSP) It was also established that membrane performance was independent of anolyte concentration. For this purpose, electrolysis was carried out at voltages of 3 and 6 V, in each case with an initial charge of 0.1, 1.0, 2.0, or 4.0 mol / L LiOH in the anolyte reservoir.

[0122] The mole ratio of LiOH corresponds to the weight ratio of Li as follows: 0.1mol / L=700ppm Li=2400ppm LiOH 1.0mol / L=7000ppm Li=24000ppm LiOH 2.0mol / L=14000ppm Li=48000ppm LiOH 4.0mol / L=28000ppm Li=96000ppm LiOH The results are shown in Table 2. At concentrations between 1 mol / L and 4 mol / L, there is no significant measured increase in membrane performance. At a LiOH concentration of 0.1 mol / L, there is a slight decrease in performance. Figure 4 shows the results in graphical form.

[0123] [Table 2]

[0124] Example 3 (LATSP) Electrolysis was carried out at 3 V, 4 V, and 6 V, in each case using 0.1 mol / L of the appropriate lithium salt in the recycled anolyte. At the start of the experiment, after short run times (shown in brackets), the permeabilities are of the same order of magnitude. For lithium hydroxide and lithium carbonate, the permeabilities increase with higher voltages, as expected, but for lithium chloride and lithium sulfate, the permeabilities decrease after longer run times at higher voltages.

[0125] Determination of the pH at the end of each experiment showed that the pH values ​​of the lithium chloride and lithium sulfate solutions had decreased to pH 3-4.

[0126] The measurements are shown in Table 3. Figure 5 shows the results in graphical form.

[0127] [Table 3]

[0128] Example 4 (LATSP) To investigate in more detail the effect of the pH of the recycled anolyte on membrane performance during electrolysis, comparisons were made using lithium chloride at concentrations of 0.1 mol / L and 1.0 mol / L, pH values ​​of 4 and 11, and an electrolysis voltage of 3 V. The pH was adjusted with a few drops of 1.0 mol / L lithium hydroxide solution. For both concentrations, increasing the pH resulted in increased permeability. In electrolysis using LiCl solutions without pH adjustment by lithium hydroxide, the anolyte pH steadily decreased. As a result, the permeability in these measurements is subject to error when correlated with pH because the pH could not be kept constant for long periods of time.

[0129] The results are reported in Table 4. Figure 6 shows the results in graphical form.

[0130] [Table 4]

[0131] Example 5 The effect of the pH of the recirculating anolyte was tested in a 24-hour experiment using a 1.0 mol / L LiCl solution at increasing voltage.

[0132] Low pH and increased voltage (3 to 8 V) did not result in permeability that remained stable. The pH varied with run time over the course of the experiment before settling at approximately pH 4, meaning that the permeability similarly did not achieve a constant value over the duration of the experiment.

[0133] Adjusting the pH by adding a small amount of LiOH solution stabilizes the permeability at a high level. The results, which stabilize after approximately 3-5 hours, are collated in Table 5. Figure 7 shows the results in graphical form.

[0134] [Table 5]

[0135] Example 6 (LATSP) In this experiment, the pH of the recirculating anolyte was adjusted with (Ca(OH)2), since pH adjustment with lithium hydroxide was not practical. The low solubility of calcium hydroxide makes it difficult to meter out further amounts as the pH decreased; the intermediate contained a proportion of solid material and was slightly turbid. Experiments were performed with a 0.1 mol / L lithium chloride solution adjusted to pH 12 with Ca(OH)2.

[0136] pH adjustment with Ca(OH)2 resulted in a clear increase in membrane permeability of over 50%. The results are collated in Table 6. Figure 8 shows the results in graphical form.

[0137] [Table 6]

[0138] Example 7 (LATSP) Similarly, when lithium sulfate Li2SO4 is the salt in the recirculating anolyte, this is accompanied by a decrease in pH during electrolysis and membrane damage. In this case, adjusting the pH with Ca(OH)2 does not lead to an improvement in membrane performance because sparingly soluble CaSO4 is formed, which precipitates on the membrane. Adjusting the pH with a 1.0 mol / L LiOH solution does not result in the formation of deposits on the membrane or a sudden drop in permeability, but instead improves them. The results are reported in Table 7. Figure 9 shows the results in graphical form.

[0139] [Table 7]

[0140] Example 8 (LATSP) Lithium carbonate as a salt in the anolyte behaves differently than lithium chloride and lithium sulfate. At 4 V, membrane performance is slightly lower than at 6 V. Between 8 V and 10 V, the permeability fluctuates and reaches a stable level where increasing the voltage does not increase the permeability.

[0141] This is due to the limited solubility of lithium carbonate, which only allows a maximum concentration of approximately 0.15 mol / L. As already explained in Example 2, permeability is lower at lower lithium concentrations. Furthermore, increasing the pH by adding Ca(OH) is only possible to a limited extent due to the buffering effect of LiCO. Taken together, this is the reason for the different behavior of LiCO in electrolysis experiments compared to LiCl and LiSO. The results are recorded in Table 8.

[0142] [Table 8]

[0143] Example 9 (LATSP) To minimize the loss of permeability due to the added Ca(OH)2 solution, the voltage was further pulsed. Two different pulse intervals were tested. In pulse interval 1, the voltage was turned on for 10 seconds and then off for 2 seconds. This achieved a 25% increase in permeability.

[0144] In pulse interval 2, the voltage is on for 50 seconds and off for 10 seconds, achieving a 61% improvement in permeability.

[0145] Table 9 compares a series of experiments using lithium chloride, each with a different permutation of pulse intervals 1 and 2 and pH adjustment with LiOH and Ca(OH)2. The reference is the comparative value for lithium hydroxide. The best performance here was achieved with lithium chloride and pulse interval 2 with Ca(OH)2. All experiments were performed with 0.1 mol / L LiCl, 6 V, and a cross-flow rate of 900 ml / min. The results are shown in Table 9 and in graphical form in Figure 10.

[0146] [Table 9]

[0147] Example 10 (Testing of Various LiSICon Materials) The performance of various LiSICon materials in an electrochemical process to produce lithium hydroxide and hydrogen is demonstrated through the determination of their permeability at various voltages with a basic 1.0 mol / L lithium hydroxide solution as the anolyte. The results are shown in Figure 11.

[0148] The properties of the material can be very well inferred from there, but it should also be noted that if the material is processed into a thin film, materials with lower permeability can be effectively used in the process.

[0149] The materials investigated are listed in Table 0. In the keys for Figures 11 and 12, LATSP stands for LiCGC® PW01, LATSP-AG-01 stands for LiCGC® AG01, and LATSP-SP01 stands for LiCGC® SP-01 from Ohara. LAGP stands for Ampcera materials, and LLTO stands for those from Toshima.

[0150] Alternatively, the behavior of the different ceramics can be explained by their permeance in each case (Figure 12). This representation is more appropriate when mass transport in the electrolysis cell is limited. The reason why LATSP SP01 differs from the other LiSICons investigated in this representation is probably because this material, with a thickness of 0.15 mm, is very thin and, as a result, is not as stable as the other materials investigated.

[0151] The measurements on which Figures 11 and 12 are based are shown in Table 13.

[0152] [Table 13]

[0153] Example 11 (LAGP) The basic anolyte solution was spiked with approximately 1000 ppm (g / g) of each of the following cations: sodium; potassium; magnesium; and calcium. An Ampcera LAGP membrane was used to transport lithium from the solution to the catholyte. The permeability is shown in Figure 13. Analysis by ion exchange chromatography showed that all catholytes (purified LiOH) contained less than 10 ppm of the corresponding impurity. A 5 V voltage pulse with a pulse interval T2 as described in Example 9 was used for each run.

[0154] Example 12 (LATSP) The basic anolyte was spiked with approximately 1000 ppm sodium ions. A LATSP membrane (LICGC PW01, Ohara, sintered as described above) was used to enrich the catholyte with lithium from the solution. The permeance is shown in Figure 14. The permeance in the absence of Na is shown for comparison. The cell voltage was 5 V, pulsed with a pulse interval of T2, as described in Example 9. Analysis by ion exchange chromatography showed that the purified LiOH contained less than 10 ppm sodium ions.

[0155] Ion Chromatography Analysis In Examples 11 and 12, the content of Li and Na ions in the analyte and catholyte was determined by ion exchange chromatography (IEC) as follows: Samples were filtered before measurement using a syringe filter (Chromafil® Xtra MV-20 / 25 type, pore size 0.20 μm, for aqueous and polar media).

[0156] Prior to the investigation, the IEC instrument (Metrohm IC 930 Compact, C Supp C6 250 / 4.0, standards (1.7 mM HNO3, 1.7 mM dipicolinic acid), conductivity sensor) was externally calibrated for Li and Na. The calibration lines used are shown in Figure 15 (for Na) and Figure 16 (for Li).

[0157] conclusion Experiments have shown that the permeability of the investigated membranes is worsened by the presence of lithium sulfate, lithium chloride, and lithium carbonate. However, adverse effects can also be produced by the addition of hydroxides such as Ca(OH)2, and also by LiOH, especially when the voltage is pulsed. High permeability is a prerequisite for high process efficiency. The discovered measures therefore help to run the process more efficiently. [Explanation of symbols]

[0158] 0 Electrochemical Cell 1. First Section 2 Second Section 3 membrane 4 anodes 5 cathode 6 First Electrical Lead 7. Voltage Source 8 Second Electrical Lead 9 Intermediates 10 Supplies 11 Basic compounds 12 Poor working medium 13 Wealth Working Media 14 Wastewater 15 Target product 16 Separation device H2O Water H2 Hydrogen O2 oxygen LiOH Lithium hydroxide OH - OH anion Li + Lithium-cation U Voltage I current A active area C F LiOH concentration in the feed C W LiOH concentration in wastewater C M0 LiOH concentration in the poor working medium C M1 LiOH concentration in the working medium

Claims

1. A process for producing hydrogen and lithium hydroxide, a) A step of providing a feed comprising at least water, Li cations, anions, and impurities, wherein the concentration of Li cations in the feed is C Ｆ The step of providing a feed, wherein in each case the pH of the feed is at least 200 ppm (by weight) or between 500 ppm (by weight) and 140,000 ppm (by weight), and the pH of the feed, measured at 25°C using a glass electrode, is between 2 and 9; b) A step of providing a poor working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration of lithium hydroxide in the poor working medium is C Ｍ０ The step of providing a poor working medium, which is at least 50 ppm (by weight) based on the total weight of the poor working medium; c) A step of providing a basic compound; d) A step of providing at least one electrochemical cell, the electrochemical cell having the following characteristics: i. The electrochemical cell includes a first compartment in which an anode is located; ii. The electrochemical cell includes a second compartment in which a cathode is located; iii. The electrochemical cell includes a membrane that separates the first membrane from the second membrane and has an area A; iv. The film comprises an inorganic material that is conductive to Li ions and electrically insulating; e) Providing at least one voltage source connected to the anode via a first electrical lead and to the cathode via a second electrical lead; f) A step of weighing the basic compound into the feed so that an intermediate is obtained, wherein the pH of the intermediate, measured at 25°C using a glass electrode, is between 9 and 13; g) The step of filling the first compartment with the intermediate; h) The step of filling the second compartment with the poor working medium; i) A step of charging the electrochemical cell with a voltage U drawn from the voltage source such that a current I flows between the anode and the cathode, wherein the ratio Q of the current intensity of the current I to the area A of the film is 100 A / m ２ ~500 A / m ２ During or at 150 A / m ２ ~350 A / m ２ The charging step is during this period; j) A step of drawing wastewater containing at least water, dissolved Li salts, oxygen, and impurities from the first compartment, wherein the concentration of Li ions in the wastewater C Ｗ However, based on the total weight of the wastewater, the concentration of Li ions in the feed is C Ｆ A lower step in the extraction process; k) withdrawing a rich working medium containing water, lithium hydroxide, and hydrogen from the second compartment, wherein the concentration C of lithium hydroxide in the rich working medium Ｍ１ is higher than the concentration C of lithium hydroxide in the lean working medium, based on the total weight of the rich working medium, Ｍ０ and the withdrawing step, which is a process.

2. The basic compound is Ca(OH) ２ , KOH, NaOH, LiOH and NH ４ The process according to claim 1, characterized in that selection is made from the group consisting of OH.

3. The basic compound is Ca(OH) ２ The process according to claim 2, characterized in that it is the process described above.

4. The process according to claim 1, characterized in that the pH of the intermediate, measured using a glass electrode at 25°C, is between 9 and 12.

5. The process according to claim 1, characterized in that the anion present in the feed is selected from the group consisting of sulfates, carbonates, hydroxides, chlorides, and fluorides.

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

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

8. The inorganic material is a compound of the following stoichiometric type (LATP): 【Chemistry 1】 [In the equation, 0.1 ≤ x ≤ 0.3] The process according to claim 7, characterized in that it is the process described above.

9. The inorganic material is a compound with the following stoichiometric properties (LATSP): 【Transformation 3】 [In the equation, 0.1 ≤ x ≤ 0.3 and 0.2 ≤ y ≤ 0.4] The process according to claim 7, characterized in that it is the process described above.

10. The inorganic material is a compound of the following stoichiometric type (LAGTSP): 【Transformation 6】 [In the equation, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, and 0 ≤ n ≤ 1.] The process according to claim 7, characterized in that it is the process described above.

11. The inorganic material is a compound of the following stoichiometric type (LAGTP): 【Transformation 5】 [In the equation, 0 ≤ x ≤ 1] The process according to claim 7, characterized in that it is the process described above.

12. The inorganic material is a compound (LAGP) of the following stoichiometric type: 【Chemistry 2】 [In the equation, x = 0, x = 0.2, or x = 0.4] The process according to claim 7, characterized in that it is the process described above.

13. The inorganic material is a compound (LLTO) of the following stoichiometric type: 【Chemistry 4】 [In the equation, 0 ≤ x ≤ 0.16] The process according to claim 7, characterized in that it is the process described above.

14. The following additional steps: m) Providing a separation device; n) A step of separating the lithium hydroxide from the working medium using the separation device, The process according to claim 1, including the process described in claim 1.

15. n) The step of separating the lithium hydroxide from the working medium using the separation device is, This results in the aforementioned poor working medium, As a result, b) A step of providing a poor working medium comprising water and lithium hydroxide dissolved therein, wherein the concentration of lithium hydroxide in the poor working medium is C Ｍ０ However, the step of providing a poor working medium that is at least 50 ppm (by weight) based on the total weight of the poor working medium is The separation device is used to perform the following The process according to claim 14.

16. The process according to claim 14, characterized in that the electrochemical cell and the separation device are provided in the same location.

17. The process according to claim 1, characterized in that at least the electrochemical cell is operated continuously.

18. The process according to claim 1, characterized in that hydrogen and lithium hydroxide are produced simultaneously.

19. The process according to claim 1, characterized in that the voltage drawn from the voltage source changes periodically over time.

20. The process according to claim 19, characterized in that the voltage drawn from the voltage source changes over time in a waveform, and the waveform is selected from the group consisting of a sine wave, a square wave, a triangular wave, or a sawtooth wave.

21. The waveform is square, that is, it is formed from a first wave interval in which the voltage is switched on at a constant value, and a second wave interval following the first wave interval in which the voltage is switched off, and the length of the first wave interval is λ １ The length of the second wave interval is λ ２ The relationship is as follows: λ １ =Φ * λ ２ The process according to claim 20, wherein the formula 3 < Φ < 7 applies.

22. The process according to claim 19, characterized in that the polarity of the voltage is maintained.

23. The process according to claim 1, characterized in that the dominant pH in both the first and second compartments, measured at 25°C using a glass electrode, is between 9 and 13.

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