Coated metal oxide material, and method, process, and apparatus for producing the same

Abstract

Coated metal oxide materials, methods of making the same, processes, and apparatuses are disclosed herein. In some embodiments, a method of making a coated metal oxide in a closed-loop continuous hydrothermal process includes mixing a first metal-containing solution and a first high-energy component to promote the formation of the metal oxide. The method can further include mixing an additional solution to form a coating on the metal oxide. In some embodiments, a process of making a coated metal oxide in a closed-loop system includes mixing a first metal-containing solution and a first high-energy component to promote the formation of the metal oxide and forming a coating on the metal oxide, and the process occurs in one or more reactors.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This disclosure claims priority to U.S. Provisional Application No. 63 / 330,501, filed Apr. 13, 2022, which is incorporated herein by reference. (Technical Field)

[0002] This disclosure relates to coated metal oxides, which include a metal oxide and a coating thereon. This disclosure relates to methods and apparatuses for making coated metal oxides. The coated metal oxides can be used in energy storage devices such as lithium - ion batteries and in ion - exchange technologies for the extraction and recovery of lithium.

Background Art

[0003] The growing markets for electric vehicles, portable household electrical appliances, and grid energy storage are escalating the demand for safe and renewable energy storage systems with high energy and longer cycle life. Li - ion - based batteries (LIBs) are dominant due to their high energy density and are widely recognized. However, the increasing demand regarding issues such as the driving range of electric vehicles, battery service life time, and the skyrocketing of material prices is leading LIB cathode providers to find a path towards LIB cathode production, which can produce high - performance materials that are also protected to be durable enough to maintain or exceed the expected electrochemical performance at low cost. One way to protect high - performance cathode materials is to introduce a coating that can maintain surface durability without inhibiting surface conductivity.

[0004] However, this coating may need to be uniform, precise, protective, and conductive in order to prevent a decline in electrochemical performance. At the same time, in order to appropriately address the surface issues of the evolving cathode materials, this coating must be adjustable with respect to synthesis. One way to achieve this is to utilize atomic layer deposition (ALD) for layer-by-layer controlled deposition, in which the chamber with the material is sequentially pumped down to vacuum and can be pulsed under the working process conditions with a reaction-limited precursor gas. Although post-synthesis processing using ALD is technically feasible, in many cases, the transfer of materials from one system to another is inefficient with respect to capital and operating costs. Additionally, cost issues imply that there is a need for a method to coat optimally and efficiently using small amounts of precursor gas.

[0005] Lithium is an essential metal for lithium batteries in a variety of applications including utility-scale energy storage, household electrical appliances, and electric transportation in the form of electric vehicles such as electric cars, electric trucks, electric boats, electric ships, and electric planes. Direct lithium extraction from brine is an alternative method for extracting and recovering lithium metal from a variety of brine sources such as geothermal brines, oil field brines, salt lake brines, seawater brines, and other sources. Metal oxide ion exchange materials absorb lithium ions from the liquid resource. They can then be induced to release the absorbed lithium ions. In some cases, the materials are induced to release lithium ions by pH swing using acids such as hydrochloric acid, acetic acid, nitric acid, sulfuric acid, formic acid, phosphoric acid, hydrobromic acid, chloric acid, or perchloric acid. In addition, ion exchange materials can be induced to release lithium ions using gas regeneration, where carbon dioxide is pressurized with water and contacted with the ion exchange material, which forces a pH swing and releases the lithium ions. In these methods, the ion exchange process is repeated to extract lithium ions from the liquid resource many times, functioning as a battery cathode charge and discharge without the actual transport of charge. In many cases, the metal oxide ion exchange material can be used directly in electrochemical battery applications, such as in the case of lithium manganese oxide, as an example. In the battery, the lithium ions can be transported back and forth in and out over the cycle, remaining in the electrolyte, and for lithium extraction, the extracted ions are transported in the form of a product stream. Furthermore, the extracted lithium can be further processed into chemical products such as lithium hydroxide and lithium carbonate for lithium battery manufacturing and other industries. In a similar process, the ion exchange material can be designed to extract other valuable minerals such as Mg, Ca, Ti, Mn, Co, Ni, Zn, Ba, Sr, Be, Ag, Cs, Rb, K, or Na. The benefits of coating this material can be carried over as well.

[0006] Some of the major challenges in direct lithium extraction using metal oxide ion exchange materials include material phase changes, dissolution of metal ion species, and degradation of the ion exchange materials (especially when an acidic environment is utilized to induce the movement of lithium ions out of the material). As in the case of other battery cathode materials where material durability has a direct impact on cycle life and performance, coatings can be a solution to these dissolution and degradation problems that affect the cycle life and performance of the lithium extraction materials. The coating can provide protection to the core material while maintaining and introducing conductive pathways, such that the overall direct lithium extraction process can be substantially beneficial.

[0007] In the present technical field, there is a need for a process to coat cathode materials and ion exchange materials at low cost, high flexibility, and high yield to meet the challenges of today's battery and lithium extraction industries. At the same time, in the present technical field, there is a need for a process to produce coated cathode materials and ion exchange materials using an apparatus with a limited number of reactors to enable low cost, high flexibility, and high yield to be competitive in the market. Summary of the Invention Means for Solving the Problems

[0008] The present disclosure shows an expandable and commercializable method for producing a coated metal oxide material by an apparatus combined for synthesis and coating, and the combined apparatus exhibits high efficiency, lower material consumption, and higher coating yield in continuous processes, batch processes, or both. The method enables an in-situ adjustable batch or continuous coating process.

[0009] In some embodiments, a method of making a coated metal oxide in a closed-loop continuous hot water process includes mixing a first metal-containing solution and a first high-energy component to promote the formation of the metal oxide.

[0010] In some embodiments, the method further includes mixing an additional solution that forms or dopes a coating on the metal oxide.

[0011] In some embodiments, the first high-energy component is a supercritical fluid.

[0012] In some embodiments, the method includes separating the formed metal oxide from a waste fluid, the waste fluid including unreacted components from the first metal-containing solution and the first high-energy component, and recycling the waste fluid to promote the formation of additional metal oxide.

[0013] In some embodiments, the supercritical fluid includes at least one of water, a metal-containing compound, a pH control agent, a chelating agent, or a ligating agent.

[0014] In some embodiments, the first metal-containing solution includes a metal-containing compound.

[0015] In some embodiments, the first metal-containing solution further includes at least one of water, a pH control agent, a chelating agent, or a ligating agent.

[0016] In some embodiments, the method further includes mixing a second metal-containing solution with the first metal-containing solution and the first high-energy component, the second metal-containing solution having at least one metal different from the first metal-containing solution or including a material that forms a coating on the metal oxide.

[0017] In some embodiments, the method further includes mixing a second high-energy component with the first metal-containing solution and the first high-energy component, the second high-energy component having at least one metal different from the first metal-containing solution or including a material for forming a coating on the metal oxide.

[0018] In some embodiments, forming the coating further includes depositing one or more atomic layers on the surface of the metal oxide using a metal-containing compound and an oxidizing gas.

[0019] In some embodiments, the coating includes at least one of a metal, a polymer, or a conductive material.

[0020] In some embodiments, the method further includes lithiating at least one of the metal oxide or the coating.

[0021] In some embodiments, the method further includes delithiating at least one of the metal oxide or the coating.

[0022] In some embodiments, the process of making the coated metal oxide in a closed-loop system includes mixing the first metal-containing solution and the first high-energy component to promote the formation of the metal oxide and forming a coating on the metal oxide, the process occurring in one or more reactors.

[0023] In some embodiments, mixing the metal-containing solution and the high-energy component is performed in a first reactor for forming the metal oxide, and the coating is formed in a second reactor for forming the coated metal oxide.

[0024] In some embodiments, the first reactor is an in-line reactor and the second reactor is an in-line reactor.

[0025] In some embodiments, the first metal-containing solution, the first high-energy component, or a combination thereof is prepared in a third reactor and then flowed to the first or second reactor after preparation.

[0026] In some embodiments, the third reactor is a stirring reactor.

[0027] In some embodiments, mixing the metal-containing solution, the high-energy component, and the additional solution is performed in a single reactor for forming a coated metal oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0028]

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Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0036] A coated metal oxide, a method and an apparatus for producing the same are disclosed herein.

[0037] (Coated Metal Oxide)

[0038] The coated metal oxide includes a metal oxide and a coating thereon. The coating can be disposed on the surface of the metal oxide and can partially or completely encapsulate the metal oxide. For example, in some embodiments, the coated metal oxide can have a core-shell structure, where the core comprises the metal oxide and the shell comprises the coating. The coating can be in any suitable shape, such as islands or clusters or continuous layers on the surface of the metal oxide.

[0039] The coating can include one or more of surface doping, island and / or cluster coatings, and / or conformal layers extending from the surface of the existing metal oxide, where the coating decomposes the surface portion of the existing metal oxide. In some embodiments, the coating can have multiple layers such as a surface doping layer, a layer extending from the surface of the metal oxide, or a combination thereof. In some embodiments, the coverage of the coating on the metal oxide surface can range from about 50 to about 100 percent. The coating can have a thickness ranging from about 0.2 nm to about 10 nm. The coating can have a crystalline or amorphous structure.

[0040] The metal oxide can have a particle diameter ranging from about 50 nm to about 100 μm. The particles can have various shapes such as polygons with different numbers of sides including triangles, squares, pentagons, hexagons, heptagons, octagons, nonagons, decagons and other polygons with more sides, rods, bars, cylinders, angled cylinders, rounded cylinders, planes, plates and other shaped crystals, and irregularly shaped spheres. The metal oxide can be in the form of single particles such as primary particles, in the form of secondary particles which are agglomerates of primary particles, or a combination thereof. A single particle, i.e., a primary particle, may have no grain boundaries, i.e., the particle consists of a single crystallite. In some cases, a single particle, or a primary particle, can have two or more grain boundaries, i.e., the particle is polycrystalline.

[0041] The metal oxide can be a material suitable as a cathode material for a lithium ion battery or a material for use as an ion exchange material. Exemplary metal oxides for use as cathode materials include lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel aluminum oxide, lithium cobalt aluminum oxide, lithium manganese aluminum oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel manganese aluminum oxide, lithium nickel cobalt manganese aluminum oxide, lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium cobalt phosphate, lithium iron cobalt phosphate, lithium iron manganese cobalt phosphate, or combinations thereof. In some embodiments, residual lithium compounds can be present on the surface of the cathode materials listed above. For example, the residual lithium compounds can include lithium carbonate, lithium hydroxide, lithium chloride, lithium oxide, lithium fluoride, lithium sulfate, lithium nitrate, other forms of lithium-containing chemicals, or combinations thereof. The residual compound may have a crystalline structure, an amorphous structure, or a combination thereof.

[0042] Exemplary metal oxides can be cathode precursors with little or no lithium to be used to synthesize cathode materials. Metal oxides for use as cathode precursors include cobalt oxide, manganese oxide, titanium oxide, nickel oxide, manganese titanium oxide, nickel manganese oxide, nickel cobalt oxide, manganese cobalt oxide, nickel titanium oxide, nickel aluminum oxide, cobalt aluminum oxide, manganese aluminum oxide, nickel manganese cobalt oxide, nickel cobalt aluminum oxide, nickel manganese aluminum oxide, nickel cobalt manganese aluminum oxide, iron phosphate, manganese iron phosphate, cobalt phosphate, iron cobalt phosphate, iron manganese cobalt phosphate, aluminum oxide, aluminum hydroxide, or combinations thereof. Metal oxides for cathode precursors can include one or more residual lithium compounds as disclosed herein.

[0043] Exemplary metal oxides suitable as ion exchange materials include lithium cobalt oxide, lithium manganese oxide, lithium titanium oxide, lithium nickel oxide, lithium manganese titanate, lithium nickel manganate, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel titanate, lithium nickel aluminum oxide, lithium cobalt aluminum oxide, lithium manganese aluminum oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel manganese aluminum oxide, lithium nickel cobalt manganese aluminum oxide, lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium cobalt phosphate, lithium iron cobalt phosphate, lithium iron manganese cobalt phosphate, lithium aluminum oxide, potassium lithium aluminum hydroxide, or combinations thereof. In some embodiments, residual lithium compounds can be present on the surface of the ion exchange materials listed above. For example, the residual lithium compounds can include lithium carbonate, lithium hydroxide, lithium chloride, lithium oxide, lithium fluoride, lithium sulfate, lithium nitrate, other forms of lithium-containing chemicals, and combinations thereof, which can have a crystalline structure, an amorphous structure, or a combination thereof. In some embodiments, the ion exchange materials listed above are delithiated to cobalt oxide, manganese oxide, titanium oxide, nickel oxide, manganese titanate, nickel manganate, nickel cobalt oxide, manganese cobalt oxide, nickel titanate, nickel aluminum oxide, cobalt aluminum oxide, manganese aluminum oxide, nickel manganese cobalt oxide, nickel cobalt aluminum oxide, nickel manganese aluminum oxide, nickel cobalt manganese aluminum oxide, iron phosphate, manganese phosphate, iron manganese phosphate, cobalt phosphate, iron cobalt phosphate, iron manganese cobalt phosphate, aluminum oxide, aluminum hydroxide, or combinations thereof, etc.

[0044] Exemplary materials for the coating can include carbon, metals, metal oxides, polymers, and other materials. Examples of carbon include amorphous carbon, carbon black, acetylene black, ketjen black, conductive carbon, polymer carbon residue, conductive graphite, graphite, natural graphite, artificial graphite, expandable graphite, synthetic graphite, graphite oxide, graphene oxide, graphene, wrinkled graphene, few-layer graphene, few-layered graphene, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon fibers, carbon nanofibers, or combinations thereof. Exemplary metals include aluminum, titanium, cobalt, nickel, copper, silicon, germanium, selenium, zirconium, niobium, tungsten, gallium, lithium, magnesium, strontium, barium, iron, hafnium, ruthenium, tantalum, vanadium, yttrium, manganese, and other metals. Exemplary metal oxides include aluminum oxide, titanium oxide, cobalt oxide, nickel oxide, copper oxide, silicon oxide, germanium oxide, selenium oxide, zirconium oxide, niobium oxide, tungsten oxide, gallium oxide, lithium oxide, magnesium oxide, strontium oxide, barium oxide, iron oxide, hafnium oxide, ruthenium oxide, tantalum oxide, vanadium oxide, yttrium oxide, manganese oxide, and other metal oxides. The coating can include a combination of two or more of the coating materials disclosed herein.

[0045] (Method)

[0046] A method of producing a coated metal oxide includes the synthesis of the metal oxide from a metal-containing precursor and the coating of the metal oxide to form the coated metal oxide.

[0047] Exemplary synthesis methods include co-precipitation synthesis, hydrothermal synthesis, wet solid synthesis, dry solid synthesis, plasma synthesis, molten salt synthesis, sol-gel synthesis, combustion synthesis, and other synthesis methods.

[0048] Exemplary coating methods include atomic layer deposition, plasma atomic layer deposition, chemical vapor deposition, pulsed laser deposition, physical vapor deposition, wet chemical methods, dry chemical methods, wet mixing methods, dry mixing methods, wet solid methods, and dry solid methods.

[0049] In some embodiments, a method of producing a coated metal oxide includes mixing a metal-containing solution and a high-energy component to form a metal oxide and depositing a coating on the metal oxide to form a coated metal oxide.

[0050] The metal-containing solution can include a metal-containing compound. The metal-containing solution can include a chelating agent, a complexing agent, a pH controller, a ligating agent, and combinations thereof. The metal-containing solution can include materials for a coating to form a metal oxide and a coating on the surface in one reaction. The metal-containing solution can be an aqueous solution. The metal-containing solution can be prepared at a temperature ranging from about 1 °C to about 200 °C. The metal-containing solution can be prepared at a pressure ranging from about 0.1 bar to about 500 bar.

[0051] The metal-containing compound can include cations of Al, Ti, Co, Ni, Cu, Si, Ge, Se, Zr, Nb, W, Sn, Ga, Li, Mg, Sr, Ba, Fe, Hf, Ru, Ta, C, V, Y, B, F, Na, Ca, Sc, P, S, Cr, Mn, Zn, Sr, Mo, Ag, Au, In, Sb, Ba, La, W, Bi, or combinations thereof, and anions of hydroxide salts, carbonate salts, sulfate salts, nitrate salts, chloride salts, oxide salts, fluoride salts, oxyhydroxide salts, halide salts, acetate salts, oxalate salts, citrate, or combinations thereof.

[0052] The chelating agent can include lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium bicarbonate, oxalic acid, or a combination thereof. The complexing agent can include polyacrylamide, phosphate oxide, phosphonate oxide, polycarboxylate oxide, zeolite, acetic acid, citric acid, chloric acid, lactic acid, crown ether, ethylenediamine, ethylenediaminetetraacetic acid, ethylene glycol tetraacetic acid, and glycine, ammonium hydroxide, ferric acetylacetonate, ferrous ammonium oxalate, ketone, or a combination thereof.

[0053] The pH control agent can include an acidic compound, a basic compound, or a combination thereof. The acidic compound can include acetic acid, sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, citric acid, acetylsalicylic acid, oxalic acid, or a combination thereof. The basic compound can include ammonia, sodium hydroxide, potassium hydroxide, ammonium hydroxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, lithium hydroxide, barium hydroxide, sodium bicarbonate, sodium carbonate, or a combination thereof.

[0054] The ligating agent can include lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium bicarbonate, oxalic acid, or a combination thereof.

[0055] The high-energy component can include a supercritical fluid, plasma, molten salt, or a combination thereof. The supercritical fluid can include carbon dioxide, methane, ethane, propane gas, R134A, ethylene, ammonia, argon, nitrogen, neon, hydrogen, water, or a combination thereof. The supercritical fluid can be mixed with a chelating agent, complexing agent, pH controller, ligating agent, or a combination thereof in the supercritical state or below the supercritical state (which can also be called the subcritical state). The supercritical fluid can be prepared at the temperature and pressure required to achieve the supercritical conditions of the fluid. The temperature of the supercritical fluid can range from about 100 °C to about 500 °C. The pressure of the supercritical fluid can range from about 0.1 bar to about 500 bar.

[0056] Mixing the metal-containing solution with the high-energy component can initiate the formation of metal oxides. The mixing can initiate a crystallization reaction to form metal oxides. In one embodiment, the supercritical fluid is mixed with the metal-containing solution and transitions the metal-containing solution to the supercritical state in a short period of time. The period can range from about 0.1 to about 48 hours. The period can be adjusted according to the targeted crystal size for production. In some embodiments, the transition to the supercritical state can initiate the formation of metal oxides. The mixture can be under the supercritical state or subcritical state depending on the temperature, pressure, and chemicals dissolved therein in the metal-containing solution and the supercritical fluid. The supercritical state can be used when the solubility of the metal compound in the solution is low to adjust the solubility of the metal compound in the solution, and the subcritical state can be used when the solubility of the metal compound in the solution is high. In some embodiments, the transition to the subcritical state can initiate the formation of a coating on the metal oxide, or doping of the surface of the metal oxide, or both.

[0057] Mixing can include in-line mixing, stirring, magnetic stirring, magnetic rotation, mixing, shear mixing, blade mixing, vibration, oscillation, rolling, milling, ball milling, ultrasonic, perturbation, air injection, air flow, and other mechanical mechanisms. The reactor can have a tubular shape that can be cylindrical, circular, triangular, rectangular, hexagonal, pentagonal, heptagonal, octagonal, or other types of angled tube shapes and combinations thereof to promote mixing behavior and performance. The walls of the reactor can be baffled, patterned, engraved, shaped, embossed, raised, have other types of regular and irregular shapes, or combinations thereof to promote mixing and performance.

[0058] The mixture can flow through the reactor, and the reactor can include a tubular reactor, a stirring reactor, a non-stirring reactor, an in-line reactor, or combinations thereof, which are under supercritical or subcritical conditions. The supercritical or subcritical conditions can have a temperature range extending from -40°C to 500°C. The supercritical or subcritical conditions can have a pressure range of 1 to 500 bar. In one embodiment, a supercritical fluid is injected into the metal-containing solution to generate a supercritical state in the mixture, and the reactor can be set to maintain the supercritical state in the mixture. In one embodiment, the reactor can be set to increase the temperature and pressure to enable the metal-containing solution to be under higher energy conditions for lower solubility, or the reactor can be set to decrease the temperature and pressure to convert a previous supercritical state from supercritical fluid injection to a subcritical state for higher solubility, or combinations thereof. One or more supercritical fluid injections can be combined with one or more reactors with different temperature and pressure conditions to form various metal oxides with coatings involving different structures such as single-layer coatings, multi-layer coatings, core-shell, gradient, multi-core-shell structures, etc.

[0059] One or more additional solutions can be added to the mixture during the metal oxide synthesis process or can be added to coat a coating on the formed metal oxide. For example, the additional solution can include a metal-containing solution to provide additional metals and / or different metals to the synthesis process. For example, the additional solution can include a coating material to form a coating on the formed metal oxide. Through the use of the additional solution, the temperature and / or pressure can be adjusted. In some embodiments, the additional solution can be used to lower the temperature and / or pressure of the mixture within the reactor. After including the additional solution, the mixture can flow through the reactor, and the reactor is under supercritical or subcritical conditions in a temperature range of -40°C to 500°C and a pressure range of 1 bar to 500 bar. By controlling the temperature and / or pressure by combination with another solution, the mixture within the reactor can be controlled to be in a supercritical or subcritical state because different materials in the mixture require different temperatures and / or pressures to reach the supercritical state. The use of the additional solution can control the solubility of the materials in the mixture within the reactor to provide conditions (e.g., supercritical conditions or subcritical conditions) in specific process steps to achieve desired results such as desired chemical structure, composition, particle morphology, particle size, coating, doping, or combinations thereof.

[0060] One or more additional high-energy components, such as a metal-containing solution, a carbon-containing solution, or a combination thereof, in a supercritical state, can be added to the mixture during the synthesis process of the metal oxide, or can be added to the mixture to coat a coating on the formed metal oxide. For example, the additional high-energy component can include a metal-containing compound for providing additional metals and / or different metals to the synthesis process. For example, an additional metal-containing solution in a supercritical state can include a coating material for forming a metal oxide coating on the formed metal oxide. For example, an additional carbon-containing solution in a supercritical state can include a coating material for forming a carbon coating on the formed metal oxide. Through the use of the additional high-energy component, the temperature and / or pressure of the mixture in the reactor can be controlled. In some embodiments, the additional high-energy component can increase the temperature and / or pressure of the mixture in the reactor. After the addition of the additional high-energy component, the mixture can flow through the reactor, and the reactor can include a tubular reactor, a stirring reactor, a non-stirring reactor, an in-line reactor, and combinations thereof, which are under supercritical conditions. In some embodiments, the supercritical conditions can be in a temperature range of 100°C to 500°C and a pressure range of 1 bar to 500 bar.

[0061] On the other hand, one or more additional low-energy components, such as a metal-containing solution, a carbon-containing solution, or a combination thereof, in a subcritical state, can be added to the mixture during the synthesis process of the metal oxide or to coat the formed metal oxide. For example, the additional low-energy component can include a metal-containing compound for providing additional metals and / or different metals to the synthesis process. For example, an additional metal-containing solution in a subcritical state can include a coating material for forming a metal oxide coating on the formed metal oxide. For example, an additional carbon-containing solution in a subcritical state can include a coating material for forming a carbon coating on the formed metal oxide. Through the use of the additional low-energy component, the temperature and / or pressure can be controlled. In some embodiments, the additional low-energy component can be used to lower the temperature and / or pressure of the mixture in the reactor. After the addition of the additional low-energy component, the mixture can flow through the reactor, and the reactor can include a tubular reactor, a stirred reactor, a non-stirred reactor, an in-line reactor, or a combination thereof, which are under subcritical conditions. In some embodiments, the subcritical or near-supercritical conditions can be in a temperature range of -40°C to 500°C and a pressure range of 1 bar to 500 bar. By controlling the temperature and / or pressure by combination with another solution, the mixture in the reactor can be controlled to be in a supercritical state or a subcritical state because different materials in the mixture require different temperatures and / or pressures to reach the supercritical state. The use of the additional solution can control the solubility of the materials in the mixture in the reactor to provide conditions (e.g., supercritical conditions or subcritical conditions) in specific process steps to achieve desired results such as a desired chemical structure, composition, particle morphology, particle size, coating, doping, or a combination thereof.

[0062] After the formation of a metal oxide or a coated metal oxide using the method disclosed herein, the method can include lithiation of the metal oxide or the coated metal oxide and / or deposition or further deposition of a coating onto the metal oxide or the coated metal oxide. The lithiation and coating steps can be carried out in any order, can be carried out one or more times, and can achieve desired results such as a desired lithium content in the metal oxide or a desired thickness and / or coverage rate of the coating.

[0063] The lithiation step can include a batch hydrothermal process, a continuous hydrothermal process, an annealing process, or a combination thereof. The lithiation step can include mixing with a lithium-containing chemical such as lithium carbonate, lithium hydroxide, lithium chloride, lithium oxide, lithium fluoride, lithium sulfate, lithium nitrate, and other forms of lithium chemicals, and reacting with the metal oxide or the coated metal oxide under a hydrothermal or annealing process. The hydrothermal process is in a temperature range of 100 °C to 500 °C. The hydrothermal process is in a pressure range of 1 bar to 500 bar in an oxygen, nitrogen, argon, air atmosphere, or a combination thereof. The annealing process is in a temperature range of 100 °C to 1,200 °C. The annealing process is in an oxygen, nitrogen, argon, air atmosphere, or a combination thereof.

[0064] The coating step can include one or more coating methods for deposition of the coating. The coating methods can include atomic layer deposition (ALD), chemical vapor deposition, pulsed laser deposition, and physical vapor deposition, wet chemical mixing, dry chemical mixing, dry coating, carbon coating, as well as polymer coating.

[0065] (Atomic layer deposition)

[0066] Atomic layer deposition (ALD) involves administering a metal precursor combined with a gas to a metal oxide to form a coating on the surface of the metal oxide. The coating can have a thickness in the range of 0.2 nm to 10 nm. The gas can include water (H2O), ozone (O3), or any suitable oxygen-containing gas for oxidizing the surface of the metal oxide. The metal precursor comprises Al, Ti, Co, Ni, Cu, Si, Ge, Se, Zr, Nb, W, Sn, Ga, Li, Mg, Sr, Ba, Fe, Hf, Ru, Ta, C, V, Y, B, F, Na, Ca, Sc, P, S, Cr, Mn, Zn, Sr, Mo, Ag, Au, In, Sb, Ba, La, W, Bi, or combinations thereof. The administration can be carried out over one or more cycles to achieve a desired coverage or layer thickness. The deposition temperature can range from about 20 °C to about 400 °C. Each dosage can be administered over a period of about 0.05 seconds to about 60 seconds. The exposure time can range from about 1 to about 3,600 seconds. The chamber can be purged between each dosage or periodically. In some embodiments, the atomic layer deposition method includes a stirring mechanism for stirring the metal oxide while ALD is being carried out.

[0067] The stirring mechanism includes vibration, oscillation, rolling, milling, scraping, mixing, ultrasonic, perturbation, air injection, liquid injection, air flow, liquid flow, and other mechanical mechanisms. An exemplary stirring mechanism is a ball milling mechanism that includes a rotating reaction device with a plurality of balls, and the plurality of balls comprises one or more of ZrO2, TiO2, stainless steel, and Al2O3. An exemplary stirring mechanism is a mechanical scraping mechanism, and the mechanical scraping mechanism includes a blade with a screw shape, a screw conveyor, a mixing blade, a scraping blade, a gradient blade, a tee, a rod, a bar, a barbed rod, or combinations thereof. An exemplary stirring mechanism is an air injection or air flow mechanism, and the air injection or air flow mechanism includes a nozzle for injecting a gas that includes air, N2, O2, Ar, or combinations thereof.

[0068] An exemplary ALD method is an in-line ALD method that uses a powder delivery mechanism and a stirring mechanism. The powder delivery mechanism can include a gravity-driven delivery mechanism with a stirring mechanism that includes other mechanical mechanisms, or combinations thereof, including powder transfer mechanisms involving vibration, oscillation, rolling, milling, ball milling, scraping, magnetic scraping, magnetic rotation, mixing, ultrasonic, perturbation, air injection, air flow, and screw conveyors. The powder delivery mechanism can include a stirring mechanism for transferring dry powder from one step to another through a tube or pipe beyond the inertia from gravity. The stirring mechanism can be used for purposes such as increasing the exposure of the dry powder in the ALD chamber to the metal precursor.

[0069] (Wet chemical mixing)

[0070] Wet chemical mixing can include mixing a metal-containing solution with a metal oxide, drying the mixture, and heat-treating the dried mixture to form a coating. The drying step can be carried out at a temperature of about 40 °C to about 600 °C. The heat treatment step can be carried out at a temperature of about 100 °C to about 1,200 °C in an oxygen, nitrogen, air, argon atmosphere, or combinations thereof.

[0071] The metal-containing solution can include a metal-containing chemical and a solvent. The solvent can include water, ethanol, acetone, acetonitrile, isopropanol, methanol, NMP, other water-soluble and / or water-insoluble solvents, or combinations thereof. The metal-containing chemical can include Al, Ti, Co, Ni, Cu, Si, Ge, Se, Zr, Nb, W, Sn, Ga, Li, Mg, Sr, Ba, Fe, Hf, Ru, Ta, C, V, Y, B, F, Na, Ca, Sc, P, S, Cr, Mn, Zn, Sr, Mo, Ag, Au, In, Sb, Ba, La, W, Bi, or combinations thereof. The metal-containing chemical can include metal hydroxides, metal carbonates, metal sulfates, metal nitrates, metal chlorides, metal oxides, metal fluorides, metal oxyhydroxides, metal halides, metal acetates, metal oxalates, metal citrates, and combinations thereof.

[0072] In some embodiments, the wet chemical mixing can include mixing the coating material in water and then cooling, filtering, and drying the mixture at a temperature of about 40 °C to about 600 °C. Since the wet chemical mixing is performed in water, this coating method can be integrated with a batch or continuous hot water production process to produce metal oxides coated in the combined process.

[0073] In some embodiments, the wet chemical mixing can include a continuous or batch hot water reaction, and the metal-containing solution is prepared by dissolving the metal-containing chemical in the solvent under a reaction pressure of about 1 to about 400 bar and mixing the solution with the metal oxide under a reaction pressure of about 1 to about 400 bar, where the mixture can be at a temperature of about 20 °C to about 1,000 °C, followed by cooling the mixture, filtering it, and drying it at a temperature of about 40 °C to about 600 °C.

[0074] The solution delivery mechanism can be used in wet chemical methods when the solid content in the metal-containing solution is high enough to make delivery by injection difficult and / or when solids precipitate and impede flow. The solution delivery mechanism can include a gravity-driven delivery mechanism with a stirring mechanism that includes vibration, oscillation, rolling, milling, ball milling, scraping, mixing, ultrasonic, perturbation, air injection, air flow, and other mechanical mechanisms including solid transfer mechanisms with screw conveyors, or combinations thereof.

[0075] (Carbon coating)

[0076] The carbon coating method or conductive coating method can include mixing a metal oxide and a carbon-containing compound and / or a conductive compound, drying the mixture, and annealing the dried mixture. The mixture can be in the form of an aqueous or non-aqueous solution. Drying can be carried out at a temperature of about 40°C to about 600°C. Annealing can be carried out at a temperature of about 50°C to about 1,200°C. The annealing atmosphere can include air, O2, N2, Ar, or combinations thereof.

[0077] A conductive material can be provided as an alternative to or in addition to the carbon-containing compound. The conductive material can include metals and / or ceramics. The metals can include W, Ti, Sn, Cu, Al, and / or other conductive metals. The ceramics can include PbO2, RuO2, TiN, TiB2, MoSi2, n-BaTiO3, Fe2O3, Ti2O3, ReO3, IrO2, yttrium barium copper oxide, and / or other conductive ceramics.

[0078] The carbon-containing compound can include glucose, sucrose, ethyl cellulose, nitrocellulose, polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), polyvinylidene fluoride, polytetrafluoroethylene, polyethylene oxide, carboxymethyl cellulose, amorphous carbon, carbon black, acetylene black, ketjen black, conductive carbon, polymer carbon residue, conductive graphite, graphite, natural graphite, artificial graphite, expandable graphite, synthetic graphite, oxidized graphite, graphene oxide, graphene, wrinkled graphene, few-layer graphene, several-layer graphene, multi-walled carbon nanotube, single-walled carbon nanotube, or a combination thereof.

[0079] In some embodiments, the carbon coating can include a continuous or batch hydrothermal reaction, and the water-soluble or water-insoluble carbon-containing solution dissolves the carbon-containing compound (and / or conductive material) in a solvent under a reaction pressure of about 1 to about 400 bar, mixes the solution with a metal oxide under a reaction pressure of about 1 to about 400 bar, where the mixture can be at a temperature of about 20 °C to about 1,000 °C, cools the mixture, filters it, and dries it at a temperature of about 40 °C to about 600 °C. A solution delivery mechanism can be provided if required as discussed above.

[0080] (Polymer coating)

[0081] The polymer coating method can include depositing a polymer coating on a metal oxide using atomic layer deposition, wet chemical mixing, continuous or batch hydrothermal reaction, etc.

[0082] In one embodiment, the polymer coating can include a conductive polymer and / or a binder polymer. The conductive polymer can include, but is not limited to, polypyrrole, polyaniline, and / or poly(3,4-ethylenedioxythiophene). The binder polymer can include, but is not limited to, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene oxide, ethyl cellulose, nitrocellulose, and / or carboxymethyl cellulose. The conductive coating can further include additives such as carbon nanotubes, graphene, conductive carbon, Cu, Ag, Au, Pt, and Os.

[0083] In one embodiment, a coating method using a conductive polymer and an additive includes dissolving a surfactant in a solvent by stirring at a temperature of 10°C to 50°C for 1 minute to 24 hours according to solubility, mixing the conductive polymer into the solution at a temperature of 40°C to 120°C for 1 minute to 24 hours, drying at a temperature of 80°C to 600°C for 6 to 24 hours, and collecting the coated powder by using filtration and washing. The surfactant can comprise one or more of sodium dodecyl sulfonate, benzalkonium chloride, cocamidopropyl betaine, polyvinylpyrrolidone, polyurethane, polystyrene, polyvinylidene fluoride, cetyl alcohol, polytetrafluoroethylene, ethyl cellulose, nitrocellulose, and carboxymethyl cellulose. The solvent can comprise one or more of N-methyl-2-pyrrolidinone, ethanol, isopropyl alcohol, acetone, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0084] In some embodiments, the polymer coating method includes dissolving one or more polymer-containing substances in a solvent, mixing the solution with a metal oxide, drying at a temperature of 40 to 600 °C, and heat-treating at a temperature of 100 to 1,200 °C in air, O2, N2, Ar, or a combination thereof. One or more conductive additives, if required, can be added to the solvent.

[0085] In some embodiments, the polymer coating method includes a continuous or batch hydrothermal reaction, and the water-soluble or water-insoluble carbon-containing solution dissolves one or more polymer-containing substances in a solvent under a pressure reaction of about 1 to about 400 bar, and mixes the solution with a metal oxide under a reaction pressure of about 1 to about 400 bar, wherein the mixture can be at a temperature of about 20 °C to about 1,000 °C, cooling the mixture, filtering, and drying at a temperature of about 40 °C to about 600 °C. A solution delivery mechanism can be provided if required, as discussed above.

[0086] Polymer-containing substances include, but are not limited to, polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), polyvinylidene fluoride, polytetrafluoroethylene, polyethylene oxide, ethyl cellulose, nitrocellulose, carboxymethyl cellulose, and combinations thereof.

[0087] Conductive additives include, but are not limited to, carbon nanotubes, graphene, conductive carbon, Cu, Ag, Au, Pt, Os, W, Ti, Sn, Cu, Al, PbO2, RuO2, TiN, TiB2, MoSi2, n-BaTiO3, Fe2O3, Ti2O3, ReO3, IrO2, yttrium barium copper oxide, and combinations thereof.

[0088] (Dry coating method)

[0089] Dry mixing or solid mixing can be carried out by adding a stoichiometric amount of a metal precursor to an uncoated powder material, followed by a mixing process that includes one of grinding, milling, pestle and mortar, milling, ball milling, and the metal precursor comprises one or more of Al, Ti, Co, Ni, Cu, Si, Ge, Se, Zr, Nb, W, Sn, Ga, Li, Mg, Sr, Ba, Fe, Hf, Ru, Ta, C, V, Y, B, F, Na, Ca, Sc, P, S, Cr, Mn, Zn, Sr, Mo, Ag, Au, In, Sb, Ba, La, W, Bi, or combinations thereof. The metal precursor can include a metal hydroxide, a metal carbonate, a metal sulfate, a metal nitrate, a metal chloride, a metal oxide, a metal fluoride, a metal oxyhydroxide, a metal halide, a metal acetate, a metal oxalate, a metal citrate, and combinations thereof. After mixing, the mixture can be subjected to high-temperature annealing in the range of 100 °C to 1,200 °C.

[0090] Dry mixing can include dry mixing a metal precursor with a metal oxide and heat-treating the mixture to form a coating. The dry mixing process can include grinding, milling, pestle and mortar, milling, and / or ball milling. The heat treatment step can be carried out at a temperature of about 100 °C to about 1,200 °C. The heat treatment can be carried out in air, O2, N2, Ar, or combinations thereof. The metal precursor comprises one or more of Al, Ti, Co, Ni, Cu, Si, Ge, Se, Zr, Nb, W, Sn, Ga, Li, Mg, Sr, Ba, Fe, Hf, Ru, Ta, C, V, Y, B, F, Na, Ca, Sc, P, S, Cr, Mn, Zn, Sr, Mo, Ag, Au, In, Sb, Ba, La, W, Bi, or combinations thereof. The metal precursor can include a metal hydroxide, a metal carbonate, a metal sulfate, a metal nitrate, a metal chloride, a metal oxide, a metal fluoride, a metal oxyhydroxide, a metal halide, a metal acetate, a metal oxalate, a metal citrate, and combinations thereof.

[0091] (Other method steps)

[0092] (Delithiation)

[0093] Other method steps can be included depending on the coated metal oxide being produced. For example, for a coated metal oxide used as an ion exchange material, a delithiation step can be used to remove lithium from the coated metal oxide. The removal of lithium from the metal oxide can create sites within the metal oxide that can be utilized to later extract lithium from another material or solution. Lithium can be removed by an acid etching process, and the metal oxide is exposed to acidic conditions for lithium removal.

[0094] The method need not be limited to the removal of lithium and can depend on the application. For example, if the targeted extraction species is a metal other than lithium, that metal can be removed from the metal oxide to create sites on the metal oxide that can later be utilized to extract the target species from another material or solution.

[0095] An example of a direct lithium extraction process is the extraction and recovery of lithium metal from various brine sources such as geothermal brine, oilfield brine, saline lake brine, seawater brine, and other sources. The metal oxide ion exchange material absorbs lithium ions from the liquid resource. Subsequently, the material can be induced to release the absorbed lithium ions. In these methods, the ion exchange process is repeated to extract lithium ions from the liquid resource multiple times and functions as battery cathode charging and discharging without actual transport of charge.

[0096] In some examples, the material is induced to release lithium ions by a pH swing using an acid such as hydrochloric acid, acetic acid, nitric acid, citric acid, sulfuric acid, formic acid, phosphoric acid, hydrobromic acid, chloric acid, or perchloric acid.

[0097] In other examples, the ion exchange material can be induced to release lithium ions using gas regeneration, and carbon dioxide is pressurized with water and brought into contact with the ion exchange material, which causes a pH swing and releases lithium ions.

[0098] Exemplary embodiments can include procedures in which the extracted lithium can be further processed into chemical products such as lithium hydroxide and lithium carbonate for lithium battery manufacturing and other industries.

[0099] In a similar process, the ion exchange material can be designed to extract other valuable minerals such as Mg, Ca, Ti, Mn, Co, Ni, Zn, Ba, Sr, Be, Ag, Cs, Rb, K, or Na. The benefits of coating these ion exchange materials can similarly be carried over.

[0100] (Encapsulation method)

[0101] In producing the ion exchange material, the method can include an encapsulation step, and the coated or uncoated metal oxide undergoes further synthesis to capture the metal oxide in a more useful industry-compatible format. For example, the encapsulation step can include mixing the coated or uncoated metal oxide, a solvent, one or more monomers, an initiator, a crosslinking agent, and a porogen, and heating to polymerize the one or more monomers and encapsulate the coated or uncoated metal oxide within the polymer material. In some embodiments, the polymer material can have a structure capable of targeting metal ions or capturing targeted metal ions.

[0102] (Coating during synthesis of metal oxide)

[0103] As discussed herein, the metal-containing solution and / or high-energy component can include coating materials that are provided during or immediately after the synthesis of the metal oxide and prior to the deposition step. For example, the metal-containing solution and / or high-energy component can include any of the coating materials discussed herein, such as metal-containing materials, carbon-containing materials, polymer-containing materials, metal precursors, etc.

[0104] (Process and apparatus)

[0105] The process for making the coated metal oxide can include one or more process reactors as described herein. As used herein, the term "reactor" can be a stand-alone reactor or can be part or region of another piece of equipment such as a pipe or tank. Exemplary processes for making the coated metal oxide include a batch hydrothermal process, a closed-loop continuous hydrothermal process, an open-loop continuous hydrothermal process, and combinations thereof. An exemplary apparatus for a batch hydrothermal process for producing the coated metal oxide is shown in FIG. 7. An exemplary apparatus for a closed-loop continuous hydrothermal process for producing the coated metal oxide is shown in FIG. 8.

[0106] The integrated metal oxide synthesis and coating within the process and apparatus substantially reduces the cost of the product. Although the ALD process is considered a cost-intensive process, combining the ALD process with metal oxide synthesis substantially reduces capital expenses and results in a lower overall cost of production. The continuous process has a higher productivity compared to the batch process for the hydrothermal metal oxide synthesis process as well as for ALD coating alone. Further, the closed-loop continuous hydrothermal process has lower material consumption and higher energy efficiency by using waste heat, waste water, and residual materials compared to the open-loop continuous hydrothermal process, resulting in not only environmental benefits but also lower operating costs.

[0107] Figure 1 depicts a coated metal oxide production process that is a continuous or batch process, which includes a four-step continuous or batch metal oxide production process, and each process step occurs in an individual reactor. As depicted by the flowchart in Figure 1, chemical mixing is carried out in the first reactor, followed by precursor synthesis in the second reactor, followed by lithiation in the third reactor, and followed by coating in the fourth reactor.

[0108] In some embodiments, the coated metal oxide production process can be a continuous or batch process that includes a two-step continuous or batch metal oxide production process, as depicted by the flowchart in Figure 2, where chemical mixing, precursor synthesis, and lithiation occur in the first reactor, followed by coating in the second reactor.

[0109] In some embodiments, the coated metal oxide production process can be a continuous or batch process that includes a one-step continuous or batch metal oxide production process, as depicted by the flowchart in Figure 3, where chemical mixing, precursor synthesis, lithiation, and coating occur in the first reactor.

[0110] In some embodiments, the coated metal oxide production process can be a batch process that includes a three-step batch metal oxide production process, as depicted by the flowchart in Figure 4, where chemical mixing occurs in the first reactor, followed by precursor synthesis in the second reactor, and followed by lithiation and coating in the third reactor.

[0111] In some embodiments, the coated metal oxide production process can be a batch process that includes a two-step batch metal oxide production process, as depicted by the flowchart in FIG. 5, where chemical mixing and precursor synthesis occur in a first reactor, followed by lithiation and coating in a second reactor.

[0112] In some embodiments, the coated metal oxide production process can be a batch process that includes a one-pot batch metal oxide production process, as depicted by the flowchart in FIG. 6, where chemical mixing, precursor synthesis, lithiation, and coating occur in one reactor.

[0113] Examples of the coated metal oxide production process include combinations of the above processes.

[0114] The reactors for synthesis and coating can have multiple functions including mixing, shear mixing, ball mixing, agitation, sonication, milling, ball milling, heating, annealing, calcination, drying, vacuum drying, evacuation, filtration, and other functions.

[0115] The reactors for synthesis and coating can withstand high pressure and high temperature and are corrosion-resistant such as stainless steel, stainless steel 304, stainless steel 316, stainless steel 316L, nickel-copper alloy, C400 alloy, Hastelloy, Inconel alloy, and other stainless steel alloys that resist potential corrosion issues caused by fluids and supercritical water in a supercritical state.

[0116] The reaction device has one or more ridges, waves, teeth, or blades on its inner wall and can improve the fluid dynamic characteristics related to mixing and exposure of the precursor. The three-dimensional shape on the inner wall exists to improve powder mixing and precursor exposure. The shape of the reaction device can be cylindrical, conical, cubic, rectangular parallelepiped, prism, or pyramid, and the cross-sectional shape can be square, elliptical, truncated cylindrical, truncated elliptical, triangular, circular, semi-circular, pentagonal, hexagonal, heptagonal, octagonal, nonagonal, decagonal, and rectangular. The edges can be sharp or rounded. The rotation direction of the reaction device can be aligned with the center line of the reaction device, or not aligned with the center line, or aligned in a direction that varies diversely during the rotation process.

[0117] The reaction device may include a plurality of balls, and the plurality of balls include one or more of ZrO2, TiO2, stainless steel, and Al2O3. The shapes of the balls include spherical, bar, cylinder, cone, cube, rectangular parallelepiped, prism, and pyramid.

[0118] The reaction device may include a shear mixing blade for mixing chemicals in the reaction device at a speed of 1 rpm to 10,000 rpm. The blade rotation direction can be aligned with the center line of the reaction device, or not aligned with the center, or vary diversely during the rotation process.

[0119] The system may include a heating control / sensing system, a liquid drainage system, a drying system, a vacuum system, a vacuum drying system, a solution mixing control system, a dry mixing control system, a pH control / sensing system, a pressure control / sensing system, a flow control system, a high vacuum system, a high pressure system, an ozone generation system, a plasma generation system, a supercritical water generation system, a compressed air system, an inert gas system, a precursor gasification system, a gas precursor delivery system, an electrical control system, a mechanical control system, a pneumatic valve control system, a milling control / sensing system, a ball mill control system, a shear mixing control system, and a continuous or batch process automation system.

[0120] Supercritical water can be produced by heating water in a sealed reactor, pipe, tube, container, vessel, chamber, or combinations thereof, from room temperature to a pressure of 0.1 to 500 bar and a temperature of 20 to 900 °C. The supercritical water heater can use electric power output, or gas output, or combinations thereof. The supercritical water heater can be connected to a heat exchanger and use waste heat to maintain or heat the supercritical water.

[0121] One or more heat exchangers can be utilized in the synthesis and coating processes to collect waste heat for the synthesis and coating processes and reuse it. Heat exchangers can have a cooling function since they collect waste heat. Heat exchangers can be tubes, crucibles, jars, containers, drums, baskets, pipes, and combinations thereof.

[0122] An example of using waste heat is to generate electricity. Another example of using waste heat is to superheat water for use within the synthesis and coating processes. Another example of using waste heat is to directly heat other parts and components within the system, such as pipes, powders, tubes, water, solutions, chemicals, precursors, fixtures, mixers, reactors, containers, chambers, and combinations thereof. The reuse or recycling of waste heat can improve the overall energy efficiency of the synthesis and coating processes and reduce the overall energy consumption.

[0123] After the synthesis and coating processes, unused materials and water can be collected. One example is extracting lithium from filtered water after hydrothermal synthesis. This can be lithium in solid form such as lithium carbonate, lithium hydroxide, lithium chloride, lithium oxide, lithium fluoride, lithium sulfate, lithium nitrate, and other forms of lithium chemicals, or this can be a lithium-containing solution having lithium in the form of the lithium chemicals enumerated above dissolved in water. Other metals such as nickel, cobalt, iron, manganese, aluminum, and other metals used in the synthesis process dissolved in the filtered water can also be extracted or reused in the manner described for lithium. The wastewater can be used after the metal extraction process. In some cases, the wastewater can be further purified. This reuse or recycling of wastewater and materials can reduce the overall material consumption and can improve the overall yield of the synthesis and coating processes.

[0124] An example of reducing the total energy consumption by the process is the reduction of the processing required after the material particles are synthesized. The process stream requires fewer instances of heat application during the synthesis of the coated material as separate steps are combined to reduce the overall energy usage. This example is evident in the reduction to a single and continuous step of a conventional process consisting of three steps, namely precursor synthesis, lithiation, and washing. The removal of the growth step using high-temperature annealing, which is replaced by drying, significantly contributes to the energy reduction. An example of the drying step can use a spray drying or granulation process. Additional examples of the drying step can include a vibrating drying method or a fluidized bed method.

[0125] Figure 7 depicts a schematic diagram of a batch hydrothermal reactor for producing a coated metal oxide according to some embodiments. The batch reactor includes an inlet 71, an outlet 72, a stirring mechanism 73, and a stirring blade 74. The inlet 71 can be used to provide the reactor with a metal-containing solution, an additional solution, a high-energy component, a supercritical fluid, a chelating agent, a complexing agent, a ligating agent, and other compounds disclosed herein. The outlet 72 can be used to transfer materials from the reactor to another device such as depicted in Figure 8. For example, the outlet 72 can be connected to cooling, heat exchange, filtration, drying, and / or ALD coating.

[0126] Figure 8 depicts an exemplary apparatus of a closed-loop continuous hydrothermal process for producing a coated metal oxide according to some embodiments. The apparatus includes a closed-loop portion and an in-line portion. In operation, the metal oxide can be formed within the closed-loop portion and then coated within the in-line portion, which is downstream of a filter 810. The apparatus includes a first inlet 81 and a second inlet 82, and valves 83 and 84 control the fluid flow through inlets 81 and 82, respectively. Inlets 81 and 82 can be used to introduce a metal-containing solution or another solution into the apparatus. For example, the other solution can be another metal-containing solution, a coating solution, a high-energy component, and / or combinations thereof.

[0127] In the case of uncoated metal oxide synthesis, one of the first or second inlets 81, 82 may not be required because another solution (additional solution) may not be needed. When the first metal-containing solution has both a metal chemical and a coating material, one of the first or second inlets 81, 82 may not be required because one inlet can deliver both the metal chemical and the coating material. For example, in this case, a single reactor (e.g., a closed-loop section) can function as both a reactor for metal oxide synthesis and a reactor for coating the metal oxide. In this context, the exemplary closed-loop continuous process depicted in FIG. 8 includes the reactor after inlets 81 and 82, although a single reactor with a single inlet or multiple reactors with multiple inlets can be provided depending on the targeted metal oxide and coating.

[0128] The apparatus includes a solution delivery mechanism 85, a heater 86, a heat exchanger 811, and a waste treatment system 88. The mixture passing through the heat exchanger 811 can be recirculated to return through the apparatus via the fluid inlet 87. The mixture can be filtered on a filter 810 to collect products such as metal oxides. The fluid from the filtration process is provided to the waste treatment system 88 and can be removed from the apparatus through an outlet 89 after treatment by the system 88 or recirculated to return into the apparatus. The fluid from the filtration process can include a metal-containing solution, high-energy components, and / or unreacted components from another solution (such as a coating solution, a lithiated solution, etc.). After the filter 810, the apparatus includes a dryer 812. For example, the product collected from the filter 810 can be dried by the dryer 812. The product collected from the filter 810 can be further processed as depicted in FIG. 8. The product can flow through a tube including a series of alternating valves 813, 814, and 816 and inlets 818, 819. The tube can include a powder delivery mechanism 820. The tube can be attached to a pump 817. The inlets 818, 819 can be used to provide additional materials to the product. For example, the inlets 818, 819 can provide materials for an ALD process.

[0129] Exemplary embodiments may include one or more controllers. In some embodiments, a controller may include one or more processors such as a processor. A processor may include, for example, a microprocessor, a microcontroller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), or any other digital or analog circuitry configured to interpret and / or execute program instructions and / or process data. In some embodiments, the processor may be communicatively coupled to a memory. The processor may be configured to interpret and / or execute non-transitory program instructions and / or data stored in the memory. The program instructions or data may constitute a portion of software for performing fluid system modeling as described herein. The memory may include any system, device, or apparatus configured to hold and / or store one or more memory modules. For example, the memory may include read-only memory, random access memory, solid-state memory, or disk-based memory. Each memory module may include any system, device, or apparatus (e.g., a computer-readable non-transitory medium) configured to hold program instructions and / or data over a period of time.

[0130] Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the disclosure. The components of the systems and apparatuses may be integrated or separated. Further, the operations of the systems and apparatuses may be performed by more, fewer, or other components. Additionally, the operations of the systems and apparatuses may be performed using any suitable logic, including software, hardware, and / or other logic. As used herein, "each" refers to each constituent of a set or each constituent of a portion of a set.

[0131] Modifications, additions, or omissions can be made to the methods described herein without departing from the scope of the present invention. For example, steps can be combined, modified, or deleted where appropriate, and additional steps can be added. Additionally, steps can be performed in any suitable order without departing from the scope of the present disclosure.

[0132] The present invention has been described using several embodiments, but numerous changes, variations, alterations, modifications, and adaptations can be proposed to those skilled in the art, and the present invention is intended to embrace such changes, variations, alterations, modifications, and adaptations as being within the scope of the appended claims. Accordingly, the present invention is clearly adapted to achieve not only the stated objects and advantages but also those inherent therein. The specific embodiments disclosed above are illustrative only, as the present invention can be modified and practiced in different but equivalent manners that will be apparent to those skilled in the art having the benefit of the teachings herein. Further, no limitation is intended with respect to the details of construction or design shown herein other than as described in the claims below. Thus, it is clear that the specific illustrative embodiments disclosed above can be modified or altered, and all such variations are considered to be within the scope and spirit of the present invention. Moreover, the terms in the claims have their plain ordinary meaning unless explicitly and clearly defined otherwise by the patentee. As used in the claims, the indefinite articles "a" or "an" are each defined herein to mean "one or more than one" of the elements introduced thereby.

[0133] Some examples have been described. However, it should be understood that various modifications can be made. Therefore, other implementations are also within the scope of the following claims.

Claims

1. A method for producing a coated metal oxide in a closed-loop continuous hot water process, the method comprising: mixing a first metal-containing solution and a first high-energy component to promote the formation of a metal oxide.

2. The method according to claim 1, further comprising mixing an additional solution to form a coating on the metal oxide.

3. The method according to claim 1, wherein the first high-energy component is a supercritical fluid.

4. Separating the formed metal oxide from a waste fluid, the waste fluid comprising unreacted components from the first metal-containing solution and the first high-energy component, and recycling the waste fluid to promote the formation of additional metal oxide. The method according to claim 1, further comprising.

5. The method according to claim 3, wherein the supercritical fluid comprises at least one of water, a metal-containing compound, a pH control agent, a chelating agent, a complexing agent, or a ligating agent.

6. The method according to claim 1, wherein the first metal-containing solution comprises a metal-containing compound.

7. The method according to claim 1, wherein the first metal-containing solution further comprises at least one of water, a pH control agent, a chelating agent, a complexing agent, or a ligating agent.

8. The method according to claim 1, further comprising mixing a second metal-containing solution with the first metal-containing solution and the first high-energy component, the second metal-containing solution having at least one metal different from the first metal-containing solution or comprising a material for forming a coating on the metal oxide.

9. further comprising mixing a second high-energy component with the first metal-containing solution and the first high-energy component, wherein the second high-energy component has at least one metal different from the first metal-containing solution or comprises a material for forming a coating on the metal oxide, the method according to claim 6.

10. Forming the coating further comprises depositing one or more atomic layers on the surface of the metal oxide using a metal-containing compound and an oxidizing gas, the method according to claim 1.

11. The coating comprises at least one of a metal, a polymer, or a conductive material, the method according to claim 1.

12. The method according to claim 1 further comprising lithiating at least one of the metal oxide or the coating.

13. The method according to claim 10 further comprising delithiating at least one of the metal oxide or the coating.

14. A process for producing a coated metal oxide in a closed-loop system, the process comprising: mixing a first metal-containing solution and a first high-energy component to promote the formation of a metal oxide; forming a coating on the metal oxide; and the process occurs in one or more reactors.

15. Mixing the metal-containing solution and the high-energy component is carried out in a first reactor for forming a metal oxide, and the coating is formed in a second reactor for forming a coated metal oxide, the process according to claim 14.

16. The process according to claim 15, wherein the first reaction device is an in-line reaction device and the second reaction device is an in-line reaction device. **Claim 17** The process according to claim 15, wherein the first metal-containing solution, the first high-energy component, or a combination thereof is prepared in a third reaction device and then flowed to the first reaction device or the second reaction device after preparation. **Claim 18** The process according to claim 17, wherein the third reaction device is a stirring reaction device. **Claim 19** The process according to claim 14, wherein mixing the metal-containing solution, the high-energy component, and the additional solution is carried out in a single reaction device for forming a coated metal oxide.

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