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  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/14—Alkali metal compounds
  • C25B1/16—Hydroxides
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  • C01—INORGANIC CHEMISTRY
  • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
  • C01D15/00—Lithium compounds
  • C01D15/02—Oxides; Hydroxides
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  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/02—Hydrogen or oxygen
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  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
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  • C25B11/042—Electrodes formed of a single material
  • C25B11/046—Alloys
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  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B15/00—Operating or servicing cells
  • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
  • C25B15/081—Supplying products to non-electrochemical reactors that are combined with the electrochemical cell, e.g. Sabatier reactor
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  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/09—Fused bath cells
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  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
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  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
  • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
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  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/80—Compositional purity

Definitions

• This application relates to the field of lithium chloride preparation technology. Specifically, it relates to a method and device for preparing high-purity lithium hydroxide based on lithium ion solid electrolyte.
• Lithium hydroxide is an important material for many lithium products, and is widely used in the preparation of lithium-based lubricants, positive electrode materials of ternary lithium battery, and additives in electrolytes of alkaline battery, etc. With the rapid development of the new energy industry in recent years, ternary electrode materials have attracted widespread attention due to their high energy density and other advantages. As a key basic material, the demand for lithium hydroxide has significantly increased globally. China's lithium resources are mainly concentrated in salt lake brine, with lithium resources in salt lakes in Qinghai and China accounting for about 80%of the total lithium resources in China. However, salt lake lithium resources generally have the characteristics of low lithium content, high magnesium-lithium ratio, and fragile surrounding ecological environment, making it difficult to develop and utilize these resources.
• CN202210731726.7 discloses a method for preparing lithium hydroxide and boron acid by high-magnesium-to-magnesium ratio brine.
• the method includes deep purification of the rich lithium brine obtained, and then using bipolar membrane electrodialysis technology to treat the refined rich lithium brine, thus obtaining an alkaline solution containing lithium hydroxide and sodium hydroxide in the alkali chamber, a dilute acid solution in the acid chamber, and a high-boron salt solution in the salt chamber.
• the crude lithium hydroxide product is obtained by separating lithium hydroxide and sodium hydroxide from the alkaline solution, and the battery-grade lithium hydroxide product is obtained by evaporation, centrifugation, washing, and drying of the crude lithium hydroxide product.
• CN202210446706.5 discloses a method for preparing lithium hydroxide from lithium waste materials, including the following steps: Stage 1: collect the lithium waste materials and allow them to air-dry to obtain stable lithium materials; Stage 2: dissolve the stable lithium materials in acid to obtain a lithium-containing leaching solution; Stage 3: adjust the pH of the lithium-containing leaching solution to 7-8, purify it to obtain a first purified solution; Stage 4: perform cold crystallization to separate saltpeter and a second purified solution from the first purified solution; Stage 5: refine, concentrate and crystallize the second purified solution with a chelating agent to obtain lithium hydroxide.
• CN202210229992. X discloses a method for producing battery-grade lithium hydroxide by recycling waste ternary lithium batteries. The method involves mixing and roasting pre-treated waste ternary positive electrode powder with sulfate to convert lithium into soluble lithium sulfate, followed by leaching with pure water to obtain a lithium-containing solution. The water leaching solution is then processed through a series of procedures including lithium salt transformation, impurity removal, evaporation, and crystallization to produce lithium hydroxide.
• CN202210073174.5 discloses a method for preparing lithium hydroxide from lithium tailings of salt lake.
• the method includes: (1) adding calcium hydroxide to the lithium tailings, heating and stirring, filtering, and taking the liquid to obtain a first treatment solution; (2) adding oxalic acid to the first treatment solution, heating and stirring, filtering, and taking the liquid to obtain a second treatment solution; (3) adding barium hydroxide to the second treatment solution, heating and stirring, filtering, and taking the liquid to obtain a third treatment solution; (4) adding sodium hydroxide to the third treatment solution, heating and stirring, filtering, and taking the liquid to obtain a fourth treatment solution; (5) evaporating and drying the fourth treatment solution to obtain a solid mixture; (6) heating the solid mixture to 650-700°C, filtering, taking the liquid, cooling to 400-450°C, filtering, and taking the solid to obtain lithium chloride; (7) electrolyzing the lithium chloride to obtain lithium hydroxide.
• CN201910381141.5 discloses a method for directly electrolyzing lithium chloride to prepare battery-grade lithium hydroxide.
• the method includes refining the lithium chloride solution, adding the refined lithium chloride solution to the anode chamber of a bipolar natural circulation ion membrane electrolysis cell, where the ion exchange membrane of the bipolar natural circulation ion membrane electrolysis cell is a cation exchange membrane.
• a lithium hydroxide solution with a mass percentage concentration of 5.5%-7.5% is added to the cathode chamber of the bipolar natural circulation ion membrane electrolysis cell, followed by the addition of pure water to adjust the mass percentage concentration of the lithium hydroxide solution to 4.9%-6.5%.
• the present disclosure requires lower-grade materials, allowing for the use of lithium salt as material, which can effectively separate lithium and magnesium. Moreover, the present disclosure only requires small amount of chemical reagent, and the electrolysis process does not generate chlorine, thereby eliminating environmental pollution and safety hazards. This method can be applied to the development and utilization of lithium resources, including salt lake brine.
• CN201410175543.7 discloses a method for preparing lithium hydroxide by electrolyzing brine from salt lakes, including the following steps: (1) concentrating the original brine containing lithium through solar evaporation in a salt field to obtain brine with a high magnesium-lithium ratio; (2) refining the high magnesium-lithium ratio brine after impurity removal; (3) using the refined brine as the anode liquid and using the lithium hydroxide solution as the cathode liquid for electrolysis, obtaining a lithium hydroxide monohydrate solution through a cation exchange membrane in the cathode chamber; (4) concentrating the lithium hydroxide monohydrate solution through evaporation, cooling, crystallization, washing and drying to obtain lithium hydroxide monohydrate.
• the technology has high requirements for materials, requiring the concentration and impurity removal of salt lake brine before use, and the electrolysis process generates chlorine, posing environmental and safety risks.
• the present disclosure has lower requirements for materials, can use low-purity lithium salt as materials, can effectively separate lithium and magnesium, requires fewer chemical reagents, and the electrolysis process does not generate chlorine, which is environmentally friendly and pollution-free.
• US20210324527A1 discloses a method for preparing lithium hydroxide, comprising: providing a mixture of lithium chloride and water to an electrolytic reaction chamber, wherein the electrolytic reaction chamber comprises an ion-selective membrane separating a first volume from a second volume, wherein the ion-selective membrane selectively allows lithium ions to pass through while inhibiting hydroxide and chloride ions from passing through the membrane; an anode located in the first volume; and a cathode located in the second volume, wherein the mixture is provided to the first volume; water or a lithium hydroxide aqueous solution is provided to the second volume; a selected voltage is provided from a power source to the anode and cathode, producing chlorine from the first volume, producing hydrogen from the second volume, and producing a lithium hydroxide solution from the second volume.
• This technology requires high-quality electrolytic materials that impurities such as calcium and magnesium ions must be removed in advance. Chlorine is produced during the electrolysis process, posing environmental and safety risks. Moreover, the ion-selective membrane used in the device is used in an aqueous solution and can only inhibit hydroxide and chloride ions from passing through, while it cannot inhibit other metal cations from passing through, thereby affecting the purity of the electrolysis product. However, the present disclosure can directly use low-purity lithium salts as materials. The lithium ion ceramic solid-state electrolyte used has highly selective permeability for lithium ions, and impurities such as other metal cations cannot pass through, thereby ensuring the purity of the product. Additionally, the amount of chemical reagents used is small, the cost is low, and no chlorine is generated during the process, resulting in minimal environmental damages and pollution-free production.
• a method for preparing lithium hydroxide includes: in an electrolysis, reducing water vapor at a low potential in presence of lithium ions to generate LiOH by using a lithium-containing molten salt as an electrolyte material at an reaction temperature of 150°C-450°C, an electrolysis voltage of 1.5V-3V, and a current density of 1-100 mA/cm 2 , wherein a solid-state electrolyte is disposed between an anode and a cathode for the electrolysis, and the water vapor is introduced at the cathode during the electrolysis.
• the electrolysis is a one-step reaction.
• a sacrificial electrode of the anode includes one or more of aluminum, zinc, and iron.
• an inert electrode of the cathode is a porous and includes one or more of graphite, nickel, nickel-iron alloy, and platinum.
• the lithium-containing molten salt comprises impurities including one or more of potassium chloride (KCl) , sodium chloride (NaCl) , calcium chloride (CaCl 2 ) , and magnesium chloride (MgCl 2 ) .
• KCl potassium chloride
• NaCl sodium chloride
• CaCl 2 calcium chloride
• MgCl 2 magnesium chloride
• an electrolytic device for preparation of lithium hydroxide includes an anode, a cathode, and a solid electrolyte disposed between the anode and the cathode, wherein the electrolytic device is configured to use a lithium-containing molten salt as an electrolyte material and perform electrolysis at an reaction temperature of 150°C-450°C, an electrolysis voltage of 1.5V-3V, and a current density of 1-100 mA/cm 2 , wherein water vapor is introduced at the cathode during the electrolysis.
• the preparation of lithium hydroxide is a one-step reaction.
• a method for preparing lithium hydroxide includes: in an electrolysis, reducing N 2 or O 2 in presence of lithium ions to form Li 3 N or Li 2 O by using a lithium-containing molten salt as an electrolyte material at a reaction temperature of 150°C-450°C, an electrolysis voltage of 1.5V-3V, and a current density of 1-100 mA/cm 2 , wherein a solid electrolyte is placed between an anode and a cathode for electrolysis, and nitrogen or oxygen is directed to pass through the cathode in the electrolysis.
• the method further includes reacting Li 3 N or Li 2 O with water to produce lithium hydroxide monohydrate with a purity of 95.0 wt%-99.99 wt%.
• reducing N 2 or O 2 in presence of lithium ions includes directing N 2 or O 2 to pass through the cathode such that N 2 or O 2 receives electrons on an inert electrode of the cathode and the lithium ions combine with the reduced nitrogen or oxygen to form Li 3 N or Li 2 O.
• reacting Li 3 N or Li 2 O with water includes by collecting and transferring Li 3 N or Li 2 O to a hydrolysis chamber, into which water vapor is introduced, and Li 3 N or Li 2 O is hydrolyzed to form the lithium hydroxide monohydrate.
• a sacrificial electrode of the anode includes one or more of aluminum, zinc, and iron.
• an inert electrode of the cathode includes one or more of graphite, nickel, nickel-iron alloy, and platinum.
• an electrolysis device for preparing lithium hydroxide.
• the device includes: an anode, a cathode, a solid electrolyte, and a hydrolysis chamber.
• the electrolysis device is configured to reduce N 2 or O 2 in presence of lithium ions to form Li 3 N or Li 2 O by using a lithium-containing molten salt as an electrolyte material at a reaction temperature of 150°C-450°C, an electrolysis voltage of 1.5V-3V, and a current density of 1-100 mA/cm 2 , wherein the solid electrolyte is placed between the anode and the cathode for electrolysis, and nitrogen or oxygen is directed to pass through the cathode in the electrolysis.
• Li 3 N or Li 2 O is reacted with water in the hydrolysis chamber to produce lithium hydroxide monohydrate with a purity of 95.0 wt%-99.99 wt%.
• FIG. 1 shows an example configuration of an apparatus for carrying out the one-step technology according to one embodiment of the present disclosure, in which (1) represents the molten lithium salt, (2) represents the sacrificial electrode, (3) represents the sealing material, (4) represents the LLZTO, (5) represents the porous inert electrode, (6) represents the water vapor inlet, (7) represents the water vapor /hydrogen outlet, and (8) represents the lithium hydroxide collection chamber.
• FIGs. 2A and 2B show an example configuration of an apparatus for carrying out the two-step technology according to one embodiment of the present disclosure, in which (9) represents the molten lithium salt, (10) represents the sacrificial electrode, (11) represents the sealing material, (12) represents the LLZTO, (13) represents the porous inert electrode, (14) represents the nitrogen/purified air inlet, (15) represents the nitrogen/purified air outlet, (16) represents the lithium nitride/lithium oxide collection chamber, (17) represents the water vapor inlet, (18) represents the lithium nitride/lithium oxide feed, (19) represents the water vapor outlet, and (20) represents the lithium hydroxide collection chamber.
• (9) represents the molten lithium salt
• (10) represents the sacrificial electrode
• (11) represents the sealing material
• (12) represents the LLZTO
• (13) represents the porous inert electrode
• (14) represents the nitrogen/purified air inlet
• (15) represents the nitrogen/purified air outlet
• (16) represents the lithium
• FIG. 3 shows an example electrolysis apparatus, in which (21) represents the glass seal, (22) represents the LLZTO tube, (23) represents the stainless steel foam, (24) represents the water vapor inlet, (25) represents the sacrificial electrode, (26) represents the molten lithium salt, (27) represents the cathode stainless steel shell, (28) represents the water vapor/hydrogen outlet, and (29) represents the lithium hydroxide collection chamber.
• FIG. 4 shows another example electrolysis apparatus, in which (30) represents the glass seal, (31) represents the molten lithium salt, (32) represents the sacrificial electrode, (33) represents the LLZTO, (34) represents the stainless foam, (35) represents the water vapor inlet, (36) represents the water vapor/hydrogen outlet, and (37) represents the lithium hydroxide collection chamber.
• FIGs. 5A and 5B show yet another example electrolysis apparatus, in which (38) represents the glass seal, (39) represents the LLZTO, (40) represents the stainless steel foam, (41) represents the nitrogen/purified air inlet, (42) represents the sacrificial electrode, (43) represents the molten lithium salt, (44) represents the cathode stainless steel shell, (45) represents the nitrogen/purified air outlet, (46) represents the lithium nitride/lithium oxide collection chamber, (47) represents the water vapor inlet, (48) represents the lithium nitride/lithium oxide feed, (49) represents the water vapor/ammonia outlet, and (50) represents the lithium hydroxide collection chamber.
• (38) represents the glass seal
• (39) represents the LLZTO
• (40) represents the stainless steel foam
• (41) represents the nitrogen/purified air inlet
• (42) represents the sacrificial electrode
• (43) represents the molten lithium salt
• (44) represents the cathode stainless steel shell
• (45) represents the
• FIGs. 6A and 6B show yet another example electrolysis apparatus, in which (51) represents the glass seal, (52) represents the molten lithium salt, (53) represents the sacrificial electrode, (54) represents the LLZTO, (55) represents the stainless steel foam, (56) represents the nitrogen/purified air inlet, (57) represents the nitrogen/purified air outlet, (58) represents the lithium nitride/lithium oxide collection chamber, (59) represents the water vapor inlet, (60) represents the lithium nitride/lithium oxide feed, (61) represents the water vapor/ammonia outlet, and (62) represents the lithium hydroxide collection chamber.
• FIGs. 7A and 7B show the electrochemical curves for the electrolysis process carried out in the electrolysis apparatus as shown in FIGs. 6A and 6B.
• FIG. 1 shows an example configuration of an apparatus for carrying out the one-step technology according to one embodiment of the present disclosure, in which (1) represents the molten lithium salt, (2) represents the sacrificial electrode, (3) represents the sealing material, (4) represents the LLZTO, (5) represents the porous inert electrode, (6) represents the water vapor inlet, (7) represents the water vapor /hydrogen outlet, and (8) represents the lithium hydroxide collection chamber.
• FIG. 2 shows an example configuration of an apparatus for carrying out the two-step technology according to one embodiment of the present disclosure, in which (9) represents the molten lithium salt, (10) represents the sacrificial electrode, (11) represents the sealing material, (12) represents the LLZTO, (13) represents the porous inert electrode, (14) represents the nitrogen/purified air inlet, (15) represents the nitrogen/purified air outlet, (16) represents the lithium nitride/lithium oxide collection chamber, (17) represents the water vapor inlet, (18) represents the lithium nitride/lithium oxide feed, (19) represents the water vapor outlet, and (20) represents the lithium hydroxide collection chamber.
• (9) represents the molten lithium salt
• (10) represents the sacrificial electrode
• (11) represents the sealing material
• (12) represents the LLZTO
• (13) represents the porous inert electrode
• (14) represents the nitrogen/purified air inlet
• (15) represents the nitrogen/purified air outlet
• (16) represents the lithium nitride
• the present disclosure proposes a new method and apparatus for extracting and preparing high-purity lithium hydroxide from low-purity lithium salts, which has low requirements for the purity of the materials, can efficiently separate magnesium and lithium, and only uses a small amount of chemical agents and has minimal impact on the environment. It can be used for the development and utilization of lithium resources, including salt lake brines.
• the present disclosure proposes a new method and apparatus for extracting and preparing high-purity lithium hydroxide from low-purity lithium salts, which requires lower purity for materials, can efficiently separate magnesium and lithium, and has smaller chemical agent usage and ecological damages.
• the method utilizes the characteristic of high selective permeability of Li+ by lithium ion ceramic solid electrolyte, which can effectively prevent impurity ions from passing through, and realizes the production of high-purity lithium hydroxide products from low-purity lithium salt materials through reasonable electrode design.
• the reaction is carries out at a temperature of 150°C-450°C; the electrolysis voltage is between 1.5V-3V, and the current density is 1-100mA/cm 2 .
• the lithium ion ceramic solid electrolyte includes but is not limited to lithium lanthanum zirconate (LLZO) , tantalum-doped lithium lanthanum zirconate (LLZTO) , niobium-doped lithium lanthanum zirconate (LLZNO) , and lithium aluminum titanium phosphate (LATP) .
• the mass fraction of lithium in low-purity lithium salts is between 0.1%-16%, where the low-purity lithium salts may include impurities such as potassium chloride (KCl) , sodium chloride (NaCl) , calcium chloride (CaCl 2 ) , and magnesium chloride (MgCl 2 ) , among others.
• KCl potassium chloride
• NaCl sodium chloride
• CaCl 2 calcium chloride
• MgCl 2 magnesium chloride
• the present disclosure provides a method for one-step preparation of lithium hydroxide.
• the method is based on the reduction of water vapor at a low potential, combined with the reaction of lithium ions to generate LiOH.
• the process directly produces LiOH using a lithium-containing molten salt as an electrolyte material at a temperature of 150°C-450°C, with an electrolysis voltage of 1.5V-3V and a current density of 1-100mA/cm 2 .
• a solid-state electrolyte is placed between the anode and the cathode of the electrolysis, and water vapor is directed to pass through the cathode in the electrolysis.
• the sacrificial electrode plate at the electrolytic anode loses electrons to form metal cations that enter the molten salt system, and at the same time, lithium ions in the molten salt system move towards the solid electrolyte through which they can reach the electrolytic cathode.
• Water vapor is directed to pass through the cathode in the electrolysis, where H 2 O molecules are reduced to H 2 on the inert electrode by gaining electrons, leaving OH-to combine with lithium ions to form high-purity LiOH.
• the reaction is carried out at a temperature of 200°C-400°C, or 250°C-350°C, or 280°C-300°C, with an electrolysis voltage of 1.8V-2.5V, or 2.0V-2.3V, and a current density of 10-900mA/cm 2 , or 30-800mA/cm 2 , or 50-550mA/cm 2 .
• the sacrificial electrode of the anode includes but is not limited to aluminum, zinc, and iron.
• the inert electrode at the cathode is a porous electrode, including but not limited to graphite, nickel, nickel-iron alloy, and platinum.
• the lithium-containing molten salt is a low-purity lithium salt, with impurities including but not limited to potassium chloride (KCl) , sodium chloride (NaCl) , calcium chloride (CaCl 2 ) , and magnesium chloride (MgCl 2 ) .
• impurities including but not limited to potassium chloride (KCl) , sodium chloride (NaCl) , calcium chloride (CaCl 2 ) , and magnesium chloride (MgCl 2 ) .
• the mass fraction of lithium element in the low-purity lithium salt is 0.1%-16%.
• Me-ne - Me n+ ;
• the advantage of the disclosed one-step method for preparing lithium hydroxide is that it is simple and can obtain high-purity lithium hydroxide from low-concentration lithium-containing molten salts.
• the by-product is economically valuable hydrogen, and this method does not produce toxic or harmful waste to the environment.
• the present disclosure also provides an electrolysis device for the one-step preparation of lithium hydroxide.
• the device includes an anode, a cathode, and a solid electrolyte using lithium-containing molten salt as an electrolyte material and performs electrolysis at a reaction temperature of 150°C-450°C, an electrolysis voltage of 1.5V-3V, and a current density of 1-100mA/cm 2 .
• a solid electrolyte is placed between the anode and cathode, and water vapor is introduced at the cathode during electrolysis.
• the cathode is an inert porous electrode.
• the electrolytic device includes a lithium hydroxide collection chamber.
• the electrolysis device includes a water vapor inlet and a water vapor/hydrogen outlet.
• the electrolysis device includes sealing materials.
• the present disclosure also provides a method for preparing lithium hydroxide using a two-step process.
• the method includes:
• Step 1 N 2 and O 2 are reduced and combined with lithium ions to form Li 3 N or Li 2 O at low potentials use a lithium-containing molten salt as an electrolyte material at a reaction temperature of 150°C-450°C, an electrolysis voltage of 1.5V-3V, and a current density of 1-100mA/cm 2 .
• a solid electrolyte is placed between the anode and the cathode during electrolysis, and nitrogen or oxygen is directed to pass through the cathode during the reaction.
• Step 2 React the generated Li 3 N or Li 2 O with water to generate lithium hydroxide monohydrate with a purity of 95.0%-99.99%
• the sacrificial electrode plate at the anode of the electrolysis loses electrons to form metal cations that enter the molten salt system, while the lithium ions in the molten salt system move towards the solid-state electrolyte and pass through the solid-state electrolyte to reach the electrolysis cathode.
• the sacrificial electrode plate at the anode of the electrolysis loses electrons to form metal cations that enter the raw material molten salt system, while lithium ions in the molten salt system move towards the solid electrolyte and reach the electrolysis cathode through the solid electrolyte.
• nitrogen or purified air excluding CO 2 , SO x and NO x , etc.
• N 2 and O 2 molecules obtain electrons on the inert electrode of the electrolysis cathode and combine with lithium ions to form Li 3 N and Li 2 O.
• the generated Li3N or Li 2 O is collected and transferred to the hydrolysis chamber.
• Water vapor is introduced into the hydrolysis chamber, and Li 3 N and Li 2 O spontaneously are hydrolyzed to produce high-purity monohydrate lithium hydroxide with a purity of 95.0%-99.99%.
• the temperature of the electrolysis reaction is at 200°C-400°C, or 250°C-350°C, or 280°C-300°C
• the electrolysis voltage is at 1.8V-2.5V, or 2.0V-2.3V
• the current density is at 10-900mA/cm 2 , or 30-800mA/cm 2 , or 50-550mA/cm 2 .
• the sacrificial anode of the anode includes but is not limited to aluminum, zinc, and iron
• the inert electrode of the cathode includes but is not limited to graphite, nickel, nickel-iron alloy, and platinum.
• the lithium-containing molten salt in the present invention is low-purity lithium salt, with impurities including but not limited to potassium chloride (KCl) , sodium chloride (NaCl) , calcium chloride (CaCl 2 ) , magnesium chloride (MgCl 2 ) , etc.
• impurities including but not limited to potassium chloride (KCl) , sodium chloride (NaCl) , calcium chloride (CaCl 2 ) , magnesium chloride (MgCl 2 ) , etc.
• the mass fraction of lithium element in the low-purity lithium salt is 0.1%-16%.
• the preparation of monohydrate lithium hydroxide leads to the production of lithium hydroxide.
• the present disclosure provides an electrolytic device for producing lithium hydroxide by a two-step method.
• the device includes an anode, a cathode, a solid-state electrolyte, and a hydrolysis chamber.
• the electrolyte material is a molten salt containing lithium
• the first step of the electrolytic reaction is operated at a temperature of 150°C-450°C, a voltage of 1.5V-3V, and a current density of 1-100mA/cm 2 .
• a solid-state electrolyte is set between the anode and the cathode during electrolysis, and nitrogen or oxygen is introduced at the cathode.
• Li 3 N and Li 2 O undergo a second-step hydrolysis reaction.
• the cathode is an inert porous electrode.
• the electrolysis device comprises a nitrogen/oxygen (purified air inlet) inlet and a nitrogen/oxygen (purified air inlet) outlet.
• the electrolytic cell includes a lithium hydroxide collection chamber.
• the electrolysis device includes sealing materials.
• the hydrolysis chamber comprises a water vapor inlet.
• the water decomposition chamber includes a water vapor or ammonia outlet.
• the advantage of the two-step method for producing lithium hydroxide is that the process conditions are mild and safe, and high-purity lithium hydroxide can be extracted from low-concentration lithium-containing molten salt.
• the by-product, ammonia also has certain economic value, and generates no toxic or harmful waste.
• FIG. 3 shows an example electrolysis apparatus, in which LLZTO lithium-ion ceramic electrolyte tube or LLZTO tube 22 is employed as the ceramic electrolyte, and an aluminum rod is employed as the sacrificial electrode 25.
• the electrolyte material or the molten lithium salt 26 used in this example is LiCl-AlCl 3 -NaCl-KCl-MgCl 2 (molar ratio of 51.7: 43.1: 1.7: 1.7: 1.8) molten salt.
• the electrolysis reaction is carried out at a temperature of 250°C and with an electrolysis current of 50mA.
• the generated hydrogen and excess water vapor are discharged through the water vapor/hydrogen outlet 28 as by-products.
• FIG. 4 shows another example electrolysis apparatus.
• LLZTO lithium-ion ceramic electrolyte sheet ( ⁇ 22*4mm) is used as the ceramic electrolyte or LLZTO 33, and aluminum sheet is used as the sacrificial electrode 32.
• the electrolyte material is a molten lithium salt 31 consisting of LiCl-AlCl 3 -CaCl 2 -KCl-MgCl 2 (molar ratio 39.6: 39.6: 2.0: 6.5: 12.3) .
• the reacting temperature is 250°C, and the electrolysis current is 50mA.
• the lithium ions in the anode compartment enter the lithium hydroxide collection chamber 37 through the LLZTO ceramic electrolyte sheet or LLZTO 33 under the drive of an external power supply.
• the one-hydrate lithium hydroxide is collected in the lithium hydroxide collection chamber 37, with a purity of 98.2%.
• the generated hydrogen and excess water vapor are discharged through the water vapor/hydrogen outlet 36 as by-products.
• FIGs. 5A and 5B This is a description of a setup for a two-step electrolysis process, as shown in FIGs. 5A and 5B.
• the left side (FIG. 5A) of the setup is an electrolysis cell where the first step of electrolysis takes place.
• the ceramic electrolyte used is an LLZTO lithium-ion ceramic electrolyte tube 39, and the sacrificial electrode 42 is an aluminum rod .
• the electrolyte materials consist of a molten lithium salt 43, a mixture of LiCl-AlCl 3 -NaCl-CaCl 2 -MgCl 2 (molar ratio of 20.8: 37.9: 10.4: 8.5: 22.4) .
• the reacting temperature of the electrolysis cell is 250°C, and the electrolysis current is 50mA.
• Lithium ions in the anode chamber are driven by an external power source through the LLZTO ceramic electrolyte tube 39 and enter the cathode chamber 46 of the electrolysis cell.
• the lithium ions react with oxygen in the nitrogen or purified air that is introduced through the nitrogen/purified air inlet 41.
• the intermediate products, Li 3 N and Li 2 O, are collected in the electrolysis cell cathode chamber or lithium nitride/lithium oxide collection chamber 46. Excess nitrogen or purified air is discharged through the electrolysis cell outlet or the nitrogen/purified air outlet 45. The collected lithium nitride or lithium oxide is transferred to the water decomposition tank on the right side of the setup (as shown in FIG. 5B) through the feed inlet or the lithium nitride/lithium oxide feed 48.
• the resulting monohydrated lithium hydroxide is collected as a product in the lithium hydroxide collection chamber 50 of the decomposition tank and has a purity of 99.0%. Excess water vapor and generated ammonia are discharged through the water vapor/ammonia outlet 49 as by-products.
• LLZTO lithium ion ceramic electrolyte sheet or LLZTO 54 ( ⁇ 22*4mm) is used as the ceramic electrolyte, and the aluminum sheet or the sacrificial electrode 53 is used as the sacrificial anode.
• the electrolyte materials are LiCl-AlCl 3 -NaCl-KCl-MgCl 2 (molar ratio 40.2: 38.1: 7.9: 5.8: 8.0) molten lithium salt 52.
• the electrolysis cell reacts at a temperature of 300°C and with an electrolysis current of 100mA.
• lithium ions enter the lithium nitride/lithium oxide collection chamber 58 through the LLZTO ceramic electrolyte sheet or the LLZTO 54 under the drive of an external power source.
• the intermediate products Li 3 N and Li 2 O are collected in the electrolysis cell cathode compartment or the lithium nitride/lithium oxide collection chamber 58, and excess nitrogen or purified air is charged through the electrolysis cell outlet or the nitrogen/purified air outlet 57.
• the collected lithium nitride or lithium oxide is transferred to the right-side hydrolysis tank in FIG. 6B through the hydrolysis tank inlet or the lithium nitride/lithium oxide feed 60.
• the resulting monohydrate lithium hydroxide is collected in the lithium hydroxide collection chamber 62 of the hydrolysis tank as the product, with a purity of 99.9%. Excess water vapor and generated ammonia are discharged through the water vapor/ammonia outlet 61 as by-products.
• FIGs. 7A and 7B The electrolysis current and cell voltage of the two-step method for preparing lithium hydroxide electrolysis cell are shown in FIGs. 7A and 7B.
• the electrolysis voltage reached 1.8V and remained stable, indicating the formation of lithium nitride at the cathode during electrolysis.
• a noticeable purple-red solid was found on the cathode current collector, which is the solid lithium nitride.

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• 2022
  • 2022-10-09 CN CN202211227355.5A patent/CN117888123A/zh active Pending
• 2023
  • 2023-10-07 WO PCT/CN2023/123190 patent/WO2024078386A1/en unknown

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