Production of lithium oxide powder

Abstract

The present invention provides a process for preparing lithium oxide powder from a combination of lithium salts.

Description

[Technical field]

[0001] The present invention relates to a process for preparing lithium oxide powder. [Background technology]

[0002] Lithium oxide is used in lithium batteries, glasses and ceramics, and other applications. In some applications, the presence of lithium hydroxide and / or other lithium compounds as impurities in the lithium oxide is undesirable.

[0003] Many methods for producing lithium oxide are known, but most suffer from one or more drawbacks with respect to process conditions, product purity, and / or economic viability. A process that produces relatively pure lithium oxide without requiring harsh conditions or multiple steps and that is economically viable is desirable. Summary of the Invention

[0004] The present invention provides lithium oxide powders that contain lithium salts. Some of these lithium oxide powders may be somewhat stable in ambient air if the lithium salt is coated on the lithium oxide. The present invention also provides high purity lithium oxide powders that contain minimal amounts of lithium salts and are not stable in ambient air.

[0005] An embodiment of the present invention is a process for producing a powder comprising lithium oxide and a lithium salt. The process includes heating a mixture of two lithium salts at one or more temperatures ranging from about 50 degrees Celsius below the eutectic point of the mixture of two different lithium salts to a temperature below the melting point of the lithium salt having the lower melting point to form a powder comprising lithium oxide and a lithium salt. During the process, at least a portion of the gaseous by-products produced by the process are removed. Optionally, a non-reactive additive is present in the mixture of the two lithium salts.

[0006] Another embodiment of the present invention is a process for converting lithium salts present in a powder containing lithium oxide and lithium salts to lithium oxide. This process can also be viewed as a process for purifying a powder containing lithium oxide and lithium salts by converting the lithium salts present to lithium oxide. The process includes heating the powder containing lithium oxide and lithium salts at one or more temperatures ranging from about 25 degrees Celsius below the melting point of the lithium salt to about 200 degrees Celsius above the melting point of the lithium salt.

[0007] Another embodiment of the present invention includes a powder comprising lithium oxide and a lithium salt.

[0008] These and other embodiments and features of the present invention will become further apparent from the following description and appended claims. [Brief description of the drawings]

[0009] [Figure 1] 1 includes photographic images of the products of the heating step on lithium salts using various reaction parameters. [Diagram 2] 1 includes two X-ray powder diffraction patterns for a product formed according to the process of the present invention, one for a powder containing lithium oxide and lithium carbonate, and one for lithium oxide without lithium carbonate. [Diagram 3] 1 is an X-ray powder diffraction pattern for a powder containing lithium oxide and lithium carbonate formed according to the process of the present invention. [Figure 4] 1 is an X-ray powder diffraction pattern for the product formed by heating lithium hydroxide monohydrate and lithium carbonate in the absence of a non-reactive additive. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The drawings depict embodiments of certain aspects of the invention and are not intended to impose limitations on the scope of the invention.

[0011] As used throughout this document, the phrase "lithium salts" includes lithium hydroxide, which is generally considered to be a base rather than a salt.

[0012] Lithium oxide (Li 2 In a process for producing a powder containing 1,2-dichlorophenyl ether (CO) and a lithium salt, one of the two lithium salts has a higher melting point and the other lithium salt has a lower melting point. The lithium salt with the higher melting point is sometimes referred to as a high melting point lithium salt or high melting point salt. The other lithium salt is sometimes referred to as a low melting point lithium salt or low melting point salt. In this document, when a specific combination of lithium salts is mentioned, the low melting point salt is usually listed first.

[0013] Generally, both lithium salts used in the process of the present invention are capable of forming lithium oxide when heated under subatmospheric (sub)atmospheric pressure and / or in the presence of an inert gas stream or an oxygen-containing inert gas stream.

[0014] Preferred combinations of two lithium salts in the practice of the invention include lithium nitrate and lithium bromide, lithium hydroxide and lithium bromide, lithium bromide and lithium carbonate, lithium hydroxide and lithium carbonate, lithium bromide and lithium chloride, and lithium nitrate and lithium bromide. A preferred combination of lithium salts is lithium hydroxide and lithium carbonate.

[0015] In the combination of lithium salts with lithium hydroxide, the lithium hydroxide can be lithium hydroxide anhydrous or lithium hydroxide monohydrate, with lithium hydroxide monohydrate being preferred. Lithium hydroxide anhydrous is preferably prepared under an inert gas (i.e., no moisture, no CO 2 , or other species that may react with lithium hydroxide), which preferably comprises one or more inert gases, typically one or more of helium, nitrogen, and argon.

[0016] When the two lithium salts are lithium hydroxide and lithium carbonate, the lithium carbonate may be introduced into the lithium hydroxide by adding solid lithium carbonate or by forming lithium carbonate in situ. The lithium carbonate may be formed in situ by reacting a portion of the lithium hydroxide with carbon dioxide by passing carbon dioxide gas through the lithium hydroxide, which can be accomplished in about 5 minutes at about 50° C. on a laboratory scale, or by contacting the lithium hydroxide with the ambient atmosphere (air), optionally with heating, for example, for about 3 hours at about 50° C. on a laboratory scale. Another method is to contact the lithium hydroxide with air for a few minutes while simultaneously reducing the particle size of the lithium hydroxide, and when this is done, the lithium carbonate usually forms a coating on the lithium hydroxide.

[0017] The minimum amount for the high melting point lithium salt is not optimized, but may be about 0.1 wt% or more based on the total weight of the mixture of the low melting point lithium salt and the high melting point lithium salt, generally about 0.1 wt% to about 20 wt% based on the total weight of the mixture, preferably about 0.1 wt% to about 15 wt%, more preferably about 0.2 wt% to about 15 wt%, and even more preferably about 0.3 wt% to about 12 wt%. When non-reactive additives are present, these amounts refer to the total weight of the mixture including the non-reactive additives.

[0018] When the high melting point salt is lithium carbonate, a typical amount is about 0.1 wt% or more, preferably about 0.2 wt% or more, generally in the range of about 0.1 wt% to about 15 wt%, preferably about 0.1 wt% to about 12 wt%, more preferably about 0.2 to about 12 wt% based on the total weight of the mixture. It has been observed that as the amount of lithium carbonate increases, the temperature can be reduced (e.g., 410°C for 5 wt% lithium carbonate), while lower amounts of lithium carbonate generally require higher temperatures (e.g., 420°C for 1 wt% lithium carbonate).

[0019] One or both of the two lithium salts may be reduced to a desired average particle size before contacting with the other lithium salt and, if used, with the non-reactive additive. Preferably, the average particle sizes of the two lithium salts are selected to maximize the contact between the particles of the two lithium salts, and the low melting point lithium salt preferably has an average particle size larger than that of the high melting point lithium salt. The low melting point lithium salt preferably has an average particle size ranging from about 5 μm to about 700 μm, more preferably from about 10 μm to about 600 μm, even more preferably from about 15 μm to about 500 μm, and the high melting point lithium salt preferably has an average particle size ranging from about 2.5 μm to about 75 μm, more preferably from about 5 μm to about 65 μm, even more preferably from about 10 μm to about 45 μm. When carried out, particle size reduction can be achieved by conventional techniques.

[0020] The optional non-reactive additive is a material that melts above the melting point of the high melting lithium salt and does not react with either of the lithium salts in the lithium salt set, or with the lithium oxide. The non-reactive additive minimizes or prevents agglomeration of the lithium oxide formed during the process, allowing the process to be carried out at slightly higher temperatures. In some embodiments, the presence of a non-reactive additive is preferred.

[0021] Suitable non-reactive additives include lithium oxide, quartz, and inorganic oxide beads, such as silica beads or zirconia beads. The non-reactive additive is preferably lithium oxide. A mixture of any two or more non-reactive additives may be used. If the non-reactive additive is lithium oxide, no purification step is required to remove the non-reactive additive at the end of the process. If the high melting point salt is lithium carbonate, the non-reactive additive is preferably a material that melts at about 725°C or higher.

[0022] When present, the non-reactive additive is generally in an amount of about 1 wt% or more based on the total weight of the mixture, but this is not optimized. In general, the amount of the non-reactive additive is in the range of about 1 wt% to about 90 wt%. In some embodiments, the amount of the non-reactive additive is in the range of about 20 wt% to about 90 wt% based on the total weight of the mixture, preferably in the range of about 25 wt% to about 85 wt%, more preferably in the range of about 50 wt% to about 80 wt%. In other embodiments, the amount of the non-reactive additive is in the range of about 1 wt% to about 20 wt%, preferably in the range of about 3 wt% to about 17 wt%, more preferably in the range of about 5 wt% to about 15 wt% based on the total weight of the mixture.

[0023] The average particle size for the non-reactive additive is preferably in the range of about 5 μm to about 700 μm, more preferably about 10 μm to about 600 μm, and even more preferably about 15 μm to about 500 μm. In some embodiments, the average particle size of the non-reactive additive is preferably similar to or smaller than the average particle size of the low melting lithium salt. When implemented, particle size reduction can be achieved by conventional techniques.

[0024] The weight percentages for the two lithium salts and any non-reactive additives are determined, for example, from the amounts of materials weighed on a balance or scale. In some examples, for example, are lithium hydroxide and lithium carbonate, and the lithium carbonate is generated in situ, the amount of lithium carbonate is determined by X-ray powder diffraction (XRD), with the understanding that there may be some amount of error in the XRD measurement since XRD only detects crystalline phases.

[0025] The order of addition or mixing of the high melting point lithium salt, the low melting point lithium salt, and any non-reactive additives has not been found to affect the process or the results obtained, particularly when the high melting point salt is lithium carbonate formed in situ, it is preferred to mix the low melting point lithium salt and the high melting point lithium first, followed by the non-reactive additives, if used.

[0026] To mix the high melting lithium salt, the low melting lithium salt, and any non-reactive additives, any conventional method or apparatus for mixing solids, such as an acoustic mixer, a ball mill (without a gas, such as air, an inert gas, or CO 2 A liquid method for mixing the two lithium salts and / or non-reactive additives (if used) may be used when at least two of these components are soluble in the selected medium, such liquid methods include spray drying of a solution, suspension, or slurry of the components, a sol-gel process, or co-precipitation of the components from a liquid.

[0027] The two lithium salts are heated while removing at least a portion of the gaseous by-products produced by the process, typically causing the low melting lithium salt to form lithium oxide. The reaction zone is where the heating of the two lithium salts (with or without non-reactive additives) takes place. In general, the reaction zone can be an oven (e.g., a static oven), a kiln, e.g., a rotary kiln or roller hearth kiln, a furnace, e.g., a vertical furnace or a tubular furnace, or a fluidized bed, with a fluidized bed being preferred.

[0028] Heating can include any convenient method of reaching and maintaining the desired reaction temperature(s). Suitable types of heating include thermal heating, microwave heating, and light heating (e.g., with a xenon arc lamp), although more than one type of heating may be used. Thermal heating is often preferred.

[0029] Heating may be performed in a batch or continuous mode. Continuous operation can be performed, for example, by feeding a series of reaction vessels through the reaction zone. Rotary kilns and roller hearth kilns can be operated continuously by charging the two lithium salts at the inlet and operating the kiln so that the two lithium salts move through the kiln and exit the outlet continuously. Fluidized beds can also be operated continuously.

[0030] Once the mixture is formed, heating of the mixture may begin. In some embodiments, the reaction zone may already be at the desired reaction temperature. In embodiments where the reaction zone is at a temperature lower than the desired reaction temperature, the mixture is preferably heated to the desired reaction temperature at a rate of about 3° C. / min to about 100° C. / min, preferably at a rate of about 5° C. / min to about 50° C. / min, more preferably at a rate of about 8° C. / min to about 50° C. / min, and these heating rates are not optimized. When using a temperature gradient or profile, optimization of the heating rate is recommended and preferred to obtain product with minimal agglomeration.

[0031] In the process of the present invention, the formation of lithium oxide from two lithium salts is accompanied by the formation of gaseous by-products (e.g., carbon dioxide and water). Removal of the gaseous by-products shifts the reaction equilibrium toward the product (lithium oxide) and minimizes or prevents reformation of the starting materials (the two lithium salts). Removal of the gaseous by-products generally slows the reaction rate. Removal of gaseous by-products is generally accomplished by running the process under reduced (sub-atmospheric) pressure or in the presence of an inert gas stream or an oxygen-containing inert gas stream.

[0032] When used alone or as part of an oxygen-containing inert gas, the inert gas preferably comprises one or more inert gases, typically one or more of helium, nitrogen, and argon. The oxygen-containing inert gas may contain any amount of oxygen, with atmospheric amounts being convenient, for example about 21% oxygen, although more or less oxygen may be present in the oxygen-containing inert gas with no expected adverse effect on the reaction. The inert gas and oxygen-containing inert gas preferably contain only small or incidental amounts of water and / or carbon dioxide, more preferably less than about 1000 ppm water and less than about 500 ppm carbon dioxide.

[0033] When the heating of the two lithium salts (with or without the presence of a non-reactive additive) is carried out in the presence of a flow of inert gas or an oxygen-containing inert gas, the flow rate sufficient to remove enough gaseous by-products to maintain a reaction equilibrium favoring the product will vary depending on the heating equipment, the reaction temperature, and the two lithium salts present in the reaction mixture. The flow rate of the inert gas or oxygen-containing inert gas is preferably in the range of about 40 sccm to about 10,000 sccm, more preferably about 500 sccm to about 7500 sccm, and even more preferably about 1000 sccm to about 6000 sccm.

[0034] When the heating of the two lithium salts (with or without the presence of a non-reactive additive) is carried out under reduced pressure, the pressure is preferably about 608 Torr (81 kPa) or less, more preferably about 380 Torr (51 kPa) or less, even more preferably about 230 Torr (31 kPa) or less, and even more preferably about 20 Torr (2.7 kPa) or less. Optionally, an inert gas or an oxygen-containing inert gas may be fed to the reaction zone while maintaining the reduced pressure.

[0035] Once the desired temperature is reached, the mixture may be heated at that temperature for the length of time necessary to form lithium oxide from one of the lithium salts, or the temperature may be varied as necessary during the reaction. The temperature may be increased to increase the conversion rate at which lithium oxide is formed during the process. The time is affected by the reaction temperature as well as the type of reaction zone. For example, in a static oven, the reaction may take about 20 hours to complete, while in a rotary kiln, the same reaction may take only about 3 hours or less to complete.

[0036] In these processes, in localized spots, especially along the interface between the two lithium salts, the two lithium salts may be present in amounts that constitute a eutectic mixture. The temperature of the process ranges from about 50 degrees Celsius below the eutectic point of the two lithium salts to a temperature below the melting point of the lithium salt with the lower melting point. Preferably, the heating is at one or more temperatures ranging from about 20 degrees Celsius below the eutectic point of the mixture of the two different lithium salts to a temperature below the melting point of the lithium salt with the lower melting point. The lower temperature of the process may also be possible at a temperature much lower than the eutectic point of the two lithium salts, but this parameter has not been optimized. A temperature a few degrees lower than the melting point of the low melting lithium salt is preferred, since extensive melting of the low melting lithium salt is undesirable and tends to produce agglomerated powder or solids that adhere to the reaction vessel. Melting of the low melting lithium salt also causes corrosion of the reaction vessel, which adds impurities to the product.

[0037] When the two lithium salts are lithium nitrate and lithium bromide, the temperature is preferably in the range of about 178° C. to less than about 255° C., more preferably in the range of about 178° C. to about 250° C. When the two lithium salts are lithium hydroxide and lithium bromide, the temperature is preferably in the range of about 225° C. to less than about 470° C., more preferably in the range of about 225° C. to about 465° C. When the two lithium salts are lithium bromide and lithium carbonate, the temperature is preferably in the range of about 446° C. to less than about 550° C., more preferably about 446° C. to about 545° C. When the two lithium salts are lithium bromide and lithium chloride, the temperature is preferably in the range of about 471° C. to less than about 550° C., more preferably about 471° C. to less than about 545° C.

[0038] In a more preferred embodiment where the two lithium salts are lithium nitrate and lithium bromide, the temperature is preferably in the range of about 208° C. to less than about 255° C., more preferably in the range of about 208° C. to about 250° C. In a more preferred embodiment where the two lithium salts are lithium hydroxide and lithium bromide, the temperature is preferably in the range of about 255° C. to less than about 470° C., more preferably in the range of about 255° C. to about 465° C. In a more preferred embodiment where the two lithium salts are lithium bromide and lithium carbonate, the temperature is preferably in the range of about 476° C. to less than about 550° C., more preferably in the range of about 476° C. to about 545° C. When the two lithium salts are lithium bromide and lithium chloride, the temperature is preferably in the range of about 501° C. to less than about 550° C., more preferably in the range of about 501° C. to less than about 545° C.

[0039] When the two lithium salts are lithium hydroxide and lithium carbonate, the temperature is preferably in the range of about 380° C. to less than about 470° C., more preferably in the range of about 380° C. to about 460° C. In some embodiments, the temperature is preferably in the range of about 380° C. to about 425° C. In some embodiments, the temperature is varied during the process. In preferred embodiments where the temperature is varied, the temperature is slowly increased from about 380° C. to about 460° C. during the process.

[0040] In more preferred embodiments where the two lithium salts are lithium hydroxide and lithium carbonate, the temperature is preferably in the range of about 410° C. to less than about 470° C., more preferably in the range of about 410° C. to about 460° C. In some more preferred embodiments, the temperature is preferably in the range of about 410° C. to about 425° C. In some embodiments, the temperature is varied during the process. In some more preferred embodiments where the temperature is varied, the temperature is slowly increased from about 410° C. to about 460° C. during the process.

[0041] It has been determined that particle size affects the reaction time and temperature required to complete the conversion to lithium oxide, with larger particles requiring longer reaction times when the at least two lithium salts are lithium hydroxide and lithium carbonate.

[0042] It has been determined that particle size and morphology do not appear to change significantly with the process of the present invention. The particles are chemically changed from two lithium salts to lithium oxide and one lithium salt, the lithium salt likely forming a coating on the particles. The product particles are often less dense than the starting material particles.

[0043] The product of heating two lithium salts and optional non-reactive additives is a powder containing lithium oxide and one lithium salt, usually a high melting point lithium salt, and the product is usually a free flowing powder. Some of these powders containing lithium oxide and one lithium salt may be somewhat stable in ambient air if the lithium salt is coated onto the lithium oxide.

[0044] The amount of lithium salt present in the powder containing lithium oxide and lithium salt may vary anywhere from slightly less than the amount present at the beginning of the process to about 0.1 wt%, depending on the rate of reaction and the length of time in the reaction zone. Generally, the amount of lithium salt present in the powder containing lithium oxide and lithium salt is about 10 wt% or less, often about 5 wt% or less, and frequently about 3 wt% or less.

[0045] Optionally, the powder containing lithium oxide and lithium salt may be subjected to one or more particle size reduction techniques. Since particle size reduction usually makes the product more susceptible to air, it is recommended and preferred to carry out the particle size reduction under an inert gas or oxygen-containing inert gas having the above characteristics.

[0046] An advantage of the process of the present invention for forming powders containing lithium oxide and lithium salts is that no bulk melting occurs during the process, which typically prevents the introduction of impurities from the reaction vessel. The process may be a solid-state or semi-solid reaction rather than a solution or melt process. A small amount of localized melting may occur during the process, but not enough to cause observable corrosion of the reaction vessel or the introduction of detectable amounts of impurities.

[0047] Another advantage of the process of the present invention is that the product is obtained in powder form, which provides the advantage that the product of the process does not adhere to the walls of the reaction vessel, allowing easy recovery of the product.

[0048] Figure 1 shows the products of various processes for heating lithium hydroxide. Figure 1A shows the product of a process according to the invention, which is a free-flowing powder. Figure 1B shows the product of a process in which there are no non-reactive additives present, which is an agglomerated powder. Figure 1C shows the product of a process in which lithium hydroxide is heated without any other ingredients being added, which appears to be extensively melted.

[0049] The relative amounts of lithium oxide and lithium salt in the product powder containing lithium oxide and lithium salt will depend in part on the amounts of the two lithium salts present in the mixture at the beginning of the process. The lithium salt in the product powder will generally be at least about 0.1 wt% of the powder, often about 0.1 wt% to about 20 wt%, preferably about 0.3 wt% to about 20 wt%, more preferably about 0.3 wt% to about 15 wt%, and even more preferably about 0.3 wt% to about 10 wt%. Because the powder containing lithium oxide and lithium salt is not susceptible to air, and without wishing to be bound by theory, it is believed that the lithium salt forms a coating on the lithium oxide particles, possibly in a core-shell structure.

[0050] The weight percent of lithium salt and lithium oxide are determined by X-ray powder diffraction (XRD), with the understanding that XRD measurements may have some amount of error because XRD detects only crystalline phases.

[0051] The lithium salt in the powder containing lithium oxide and a lithium salt is lithium bromide, lithium carbonate, lithium chloride, or lithium iodide, and preferably the lithium salt is lithium carbonate.

[0052] 2A and 3 are X-ray powder diffraction (XRD) patterns for powders containing lithium oxide and lithium carbonate formed according to the process of the present invention as described above. 2 There is a large peak at 33.6 degrees 2θ characteristic of O and a very small peak at most at 32.5 degrees 2θ characteristic of LiOH. Figure 4 shows the XRD pattern for the product formed in the absence of the non-reactive additive, and the diffraction pattern shows a prominent peak at 33.6 degrees 2θ (LiOH). 2 O), and an even larger peak at 32.5 degrees 2θ (LiOH).

[0053] In the process of the present invention, the surfaces of the reaction vessel in contact with the reactants and products are corrosion resistant and can withstand the reactants and products (low melting lithium salts, high melting lithium salts, lithium oxide, any non-reacting The reactor vessel may be constructed from any material that is inert to the reaction vessel (e.g., the reaction vessel heat exchanger ...

[0054] When pure lithium oxide powder is desired and the lithium salt is lithium carbonate, the powder containing lithium oxide and the lithium salt is heated to a temperature ranging from about 25 degrees Celsius below the melting point of the lithium salt to about 200 degrees Celsius above the melting point of the lithium salt to form the lithium oxide powder.

[0055] If pure lithium oxide powder is desired and the lithium salt is a lithium halide, the powder containing lithium oxide and lithium salt is heated to a temperature ranging from about 25 degrees Celsius below the boiling point of the lithium salt to about 200 degrees Celsius above the boiling point of the lithium salt to form the lithium oxide powder. The lithium halide may be lithium chloride, lithium bromide, or lithium iodide.

[0056] If a non-reactive additive is used in the process to form the powder comprising lithium oxide and a lithium salt, and the non-reactive additive is not lithium oxide, the non-reactive additive is preferably removed from the powder comprising lithium oxide and a lithium salt prior to heating the powder comprising lithium oxide and a lithium salt to the desired temperature to effect conversion of the lithium salt to lithium oxide.

[0057] With respect to the process for preparing pure lithium oxide powder from a powder containing lithium oxide and a lithium salt, the amount of lithium salt present in the powder containing lithium oxide and a lithium salt is usually about 10 wt% or less, often about 5 wt% or less, and frequently about 3 wt% or less, and generally the amount of lithium salt in the powder containing lithium oxide and a lithium salt is about 0.1 wt% or more. In some embodiments, the amount of lithium salt present in the powder containing lithium oxide and a lithium salt ranges from about 0.1 wt% to about 10 wt%, or from about 0.1 wt% to about 5 wt%, or from about 0.1 wt% to about 3 wt%.

[0058] Heating a powder containing lithium oxide and a lithium salt typically converts the lithium salt to lithium oxide.

[0059] The powders containing lithium oxide and lithium carbonate are often heated to the desired reaction temperature at a rate of about 3° C. / min to about 100° C. / min, preferably at a rate of about 5° C. / min to about 50° C. / min, and more preferably at a rate of about 8° C. / min to about 50° C. / min.

[0060] Once the desired temperature is reached, the powder containing lithium oxide and lithium salt may be heated at that temperature for the length of time necessary to form lithium oxide from the lithium salt. The temperature may be varied during the process. The time is influenced in part by the reaction temperature, the temperature profile of the combination of the two lithium salts and the non-reactive additive, the reaction zone, and the amount of lithium salt present. On a laboratory scale, the reaction time ranges from about 5 minutes to about 25 hours.

[0061] The temperature of the process of heating the powder containing lithium oxide and lithium salt, when the lithium salt is lithium carbonate, ranges from about 25 degrees Celsius below the melting point of the lithium salt to about 200 degrees Celsius above the melting point of the lithium salt, preferably from about 25 degrees Celsius below the melting point of the lithium salt to about 175 degrees Celsius above the melting point of the lithium salt, more preferably from about 25 degrees Celsius below the melting point of the lithium salt to about 100 degrees Celsius above the melting point of the lithium salt. Although a temperature of about 200 degrees Celsius above the melting point of the lithium salt may be used, These temperatures do not provide any particular advantage. When the lithium salt is lithium carbonate, the temperature is preferably in the range of about 700° C. to about 900° C., more preferably in the range of about 700° C. to about 800° C., and even more preferably in the range of about 700° C. to about 750° C. In some preferred embodiments where the lithium salt is lithium carbonate, the temperature is preferably in the range of about 700° C. to about 750° C.

[0062] In the process for forming pure lithium oxide from a powder containing lithium oxide and a lithium salt, water is eliminated by heating at reduced pressure or in the presence of an inert gas or oxygen-containing inert gas, preferably a flowing inert gas or oxygen-containing inert gas, as described above for the process of heating two lithium salts.

[0063] Preferably, the process of forming pure lithium oxide from a powder containing lithium oxide and a lithium salt is carried out in the presence of a flow of inert gas or an oxygen-containing inert gas, which removes gaseous by-products from the reaction zone. The flow rate of the inert gas or oxygen-containing inert gas is preferably about 25 sccm or greater, or in the range of about 25 sccm to about 1000 sccm, more preferably about 50 sccm to about 500 sccm.

[0064] When the process is carried out under reduced pressure, the pressure is preferably not greater than about 608 Torr (81 kPa), more preferably not greater than about 380 Torr (51 kPa), even more preferably not greater than about 230 Torr (31 kPa), and even more preferably not greater than about 20 Torr (2.7 kPa). Optionally, an inert gas or oxygen-containing inert gas may be fed to the reaction zone while maintaining the reduced pressure.

[0065] The product from heating a powder containing lithium oxide and a lithium salt is a lithium oxide powder containing little or no lithium salt, the lithium oxide being air sensitive and typically a free flowing powder.

[0066] FIG. 2B is an XRD pattern for a product formed according to the process of the present invention. The diffraction pattern contains a large peak at a 2θ value of 34 degrees (Li 2 O), and no lithium carbonate peak was observed.

[0067] The following examples are presented for illustrative purposes and are not intended to impose limitations on the scope of the invention.

[0068] Some of the examples of the present invention had incomplete conversion of the low melting lithium salt to lithium oxide. In these cases, higher conversion to lithium oxide can be achieved by heating for a longer period of time and / or using a higher inert gas flow rate. EXAMPLES

[0069] Example 1 Lithium hydroxide monohydrate (LiOH H 2 O, 85 wt%) in an acoustic mixer 2 CO 3 (5wt%) and Li 2 O (10 wt%). After mixing for a few minutes at ambient temperature, the mixture was transferred to an alumina crucible and heated to 410 °C at a rate of 10 °C / min and held at 410 °C for 10 h under 60 sccm argon flow. When the temperature reached 100 °C, heat loss and weight loss were observed. Further weight loss was observed during the 10 h heating at 410 °C. The mixture was cooled to ambient temperature under argon flow to give a free-flowing powder (Figure 1A). An X-ray powder diffraction pattern was collected for a sample of the cooled product. The resulting diffraction pattern is shown in Figure 2A. The diffraction pattern contains Li 2 A large peak was observed at 33.6 degrees 2θ, which is characteristic of O. Small peaks were observed at 12 and 22 degrees 2θ. represents a small amount of Li in the product. 2 CO 3 or due to LiOH (LiOH comes from the reaction of lithium oxide with water vapor).

[0070] The product powder from the above step was heated in an alumina crucible to 700°C at a rate of 10°C / min and held at 700°C for 5 hours under argon flow at 60 sccm. Weight loss was observed during the 5 hour heating at 700°C. The mixture was cooled to ambient temperature under argon to obtain a free-flowing powder. An X-ray powder diffraction pattern was collected for a sample of the cooled product. The diffraction pattern obtained is shown in Figure 2B. The diffraction pattern contains Li 2Along with a small pair of peaks at 38 degrees due to O, 2 A large peak at 34 degrees 2θ, characteristic of LiO, was observed. 2 CO 3 No peak was observed.

[0071] Example 2 Lithium hydroxide monohydrate was exposed to air at room temperature for 3 h to form LiOH H 2 Li on O 2 CO 3 A coating of about 10 wt% Li was formed. 2 CO 3 ). Coated LiOH H 2 O was mixed with Li in an acoustic mixer. 2 O (10 wt%). After mixing for a few minutes at ambient temperature, the mixture was transferred to an alumina crucible and heated to 410 °C at a rate of 10 °C / min and held at 410 °C for 15 h under flowing argon at 60 sccm. The mixture was cooled to ambient temperature under flowing argon to give a free-flowing powder. An X-ray powder diffraction pattern was collected for a sample of the cooled product. The diffraction pattern obtained is shown in Figure 3. The diffraction pattern shows that there is a small amount of Li in the product. 2 CO 3 There are small peaks at 30.7 and 31.7 degrees 2θ due to Li 2 O) was observed.

[0072] Example 3 Lithium hydroxide monohydrate, Li 2 CO 3 (10 wt%). The mixture was heated to 410° C. in an alumina crucible at a rate of 10° C. / min and held at 410° C. for 5 hours under flowing argon at 60 sccm. The mixture was cooled to ambient temperature under flowing argon to obtain a powder. An X-ray powder diffraction pattern was collected for a sample of the cooled product. The diffraction pattern obtained is shown in FIG. 4. The diffraction pattern contains a medium sized peak at 33.6 degrees (Li 2 O), as well as a small amount of Li in the product. 2 CO 3A large peak at 32.5 degrees 2θ was observed, along with small peaks at 30.5 and 31.7 degrees 2θ due to LiOH. 2 The relative size of the O peaks indicates that LiOH is only partially 2 It was concluded that the product was not converted to O. An image of the product, an agglomerated powder, is shown in Figure 1B.

[0073] Example 4 - Comparison Lithium hydroxide monohydrate powder was heated in an alumina crucible to 480°C at a rate of 10°C / min and held at 480°C for 5 hours under argon flow at 60 sccm. 2 The conversion of LiOH to O was complete after 1 h. The product was cooled to ambient temperature under a flow of argon. The product was not a free-flowing powder. At ambient temperature, the product coated the walls of the alumina crucible. An image of the product is shown in Figure 1C. The solid was not a powder and extensive melting occurred during the process.

[0074] Example 5 Lithium hydroxide monohydrate (LiOH H 2 O, 85 wt%) in an acoustic mixer 2 CO 3 (5wt%) and Li 2 After mixing for several minutes at ambient temperature, the mixture was transferred to an alumina crucible and heated to 410° C. at a rate of 10° C. / min and held at 410° C. for 10 hours with 60 sccm flowing argon. When the temperature reached 100° C., heat loss and weight loss were observed. Further weight loss was observed during the 10 hours of heating at 410° C. The mixture was cooled to ambient temperature under flowing argon to obtain a free-flowing mixture. A powder was obtained. An X-ray powder diffraction pattern was collected on a sample of the cooled product. The diffraction pattern showed Li 2 A large peak at 33.6 degrees 2θ, characteristic of O, was observed. Small peaks at 12 and 22 degrees 2θ, corresponding to small amounts of Li in the product, were observed. 2 CO 3 or due to LiOH (LiOH comes from the reaction of lithium oxide with water vapor).

[0075] The product powder from the above step was heated in an alumina crucible to 700°C at a rate of 10°C / min and held at 700°C for 5 hours under 60 sccm argon. Weight loss was observed during the 5 hour heating at 700°C. The mixture was cooled to ambient temperature under argon to give a free-flowing powder. An X-ray powder diffraction pattern was collected for a sample of the cooled product. The diffraction pattern showed Li 2 Along with a small pair of peaks at 38 degrees due to O, 2 A large peak at 34 degrees 2θ, characteristic of LiO, was observed. 2 CO 3 No peak was observed.

[0076] Example 6 Lithium hydroxide monohydrate (LiOH H 2 O, 90 wt%) in an acoustic mixer 2 CO 3 and Li 2 Two runs were performed in which the mixture was mixed with 0.3 wt% lithium carbonate and in the other run, 0.5 wt% lithium carbonate was added, for a total of 0.4 wt% lithium carbonate and 0.6 wt% lithium carbonate. After mixing for several minutes at ambient temperature, each mixture was transferred to an alumina crucible, heated to 410° C. at a rate of 10° C. / min, and held at 410° C. for 10 hours with 60 sccm argon flow. When the temperature reached 100° C., heat loss and weight loss were observed. Further weight loss was observed during the 10 hours of heating at 410° C. The mixture was cooled to ambient temperature under argon flow to obtain a free-flowing powder.

[0077] Example 7 Lithium hydroxide monohydrate (LiOH H 2 O, 90 wt%) in an acoustic mixer 2 CO 3 and Li 2O and heated at 410°C as described in Example 6. Run 1 contained 0.1 wt% lithium carbonate, 10 wt% lithium oxide, the LiOH was not ground and the average particle size was 600 μm. Runs 2 and 3 contained 0.7 wt% lithium carbonate (with 0.6 wt% lithium carbonate added) and 10 wt% lithium oxide. In run 2, the LiOH was not ground and the average particle size was 600 μm. In run 3, the LiOH was ground to an average particle size of 10 μm. Runs 2 and 3 were held at 410°C for 20 hours.

[0078] The products of Runs 2 and 3 were heated in an alumina crucible to 800° C. at a rate of 10° C. / min and held at 800° C. for 30 minutes under flowing argon at 60 sccm. The products were cooled to ambient temperature under argon to give free-flowing powders.

[0079] Example 8 Unground lithium hydroxide monohydrate (LiOH H 2 O, 90 wt%) in an acoustic mixer with 0.2 wt% Li 2 CO 3 and 10wt% Li 2 A heating run was performed as described in Example 6, except that the mixture was mixed with 2000 mol / L and the temperature was held at 418° C. for 10 hours, then 430° C. for 5 hours, then 440° C. for 5 hours, then 450° C. for 5 hours. An X-ray powder diffraction pattern was collected on a sample of the cooled product. The diffraction pattern showed that about 1.1 wt % LiOH remained in the product, indicating that the stepwise heating results in a higher conversion to lithium oxide, at least for the conversion from lithium hydroxide.

[0080] Example 9 Lithium hydroxide monohydrate (LiOH H 2 O, 20 wt%) in an acoustic mixer with 2.65 wt% Li 2 CO 3 and 80wt% Li 2Two runs were performed in which LiOH, LiOH, and O were mixed and heated as described in Example 6, except that the temperature was 450° C., the time was 10 hours, and the crucible was Pt / Rh / alumina. In one run, the LiOH was not ground, and in the other run, the LiOH was ball milled for 20 minutes before being mixed with the other ingredients.

[0081] The powder from the run using ball-milled LiOH was partially agglomerated. X-ray powder diffraction patterns were collected on samples of the cooled product from the unmilled LiOH run. The diffraction patterns were consistent with LiOH H 2 The peaks from Li 2 X-ray powder diffraction patterns were collected on samples of the cooled product from the ground LiOH run. The diffraction patterns showed that the conversion of LiOH H 2 The peaks from O indicate contamination due to air exposure or Li 2 It indicates either that the conversion to O is incomplete.

[0082] Example 10 Li in an alumina crucible 2 CO 3 Lithium hydroxide monohydrate (LiOH H 2 A mixture of 1,2-dimethylformamide (1,2,3,4-tetramethylphenyl) and 1,2-dichlorophenyl (1,2,3,4-tetramethylphenyl) was placed in a vertical furnace set at a temperature of 450° C. (actual temperature approximately 425° C.) with flowing argon at 5 L / min (5000 sccm) for 3 hours. The mixture was cooled to ambient temperature under flowing argon to give a free-flowing powder. An X-ray powder diffraction pattern was collected on a sample of the cooled product. The diffraction pattern obtained indicated that the product was 23 wt % Li 2 O and 77 wt% LiOH.

[0083] An ingredient referred to anywhere in this specification or claims by chemical name or formula, whether referred to in the singular or plural, is identified as being present prior to contact with another substance (e.g., another component, solvent, etc.) referred to by the chemical name or chemical type. It does not matter what chemical changes, transformations, and / or reactions (if any) occur in the resulting mixture or solution, because such changes, transformations, and / or reactions are the natural result of bringing the specified ingredients together under the conditions required in accordance with this disclosure. Thus, ingredients are identified as ingredients that are brought together in connection with performing a desired operation or in forming a desired composition. Also, even if the claims herein may refer to substances, components, and / or ingredients in the present tense (such as "comprising," "is," etc.), the reference refers to the substance, component, or ingredient that was present immediately prior to being first contacted, blended, or mixed with one or more other substances, components, and / or ingredients in accordance with this disclosure. Thus, the fact that a substance, component, or ingredient may have lost its original identity by chemical reaction or change in the course of a contacting, blending, or mixing operation, when carried out in accordance with this disclosure and within the ordinary skill of a chemist, is of no practical importance.

[0084] The present invention may comprise, consist of, or consist essentially of the materials and / or procedures recited herein.

[0085] As used herein, the term "about" modifying the amount of a component in the composition or used in the method of the present invention refers to the variation in the numerical amount that may occur due to, for example, typical measuring procedures and liquid handling procedures used to make concentrates or use solutions in the real world, inadvertent errors in these procedures, differences in manufacture, source, or purity of the components used to make the composition or carry out the method. The term about also encompasses amounts that differ due to different equilibrium conditions of the composition obtained from a particular initial mixture. Whether or not modified by the term "about", the claims include the equivalent of the amount.

[0086] Unless expressly indicated otherwise, the article "a" or "an" as used herein is not intended, and should not be construed as, limiting the description or claims to the single element to which the article refers. Rather, as used herein, the article "a" or "an" is intended to cover one or more such elements, unless the context expressly indicates otherwise.

[0087] This invention is susceptible to considerable variation in its practice, and therefore the foregoing description is not intended to limit, and should not be construed as limiting, the invention to the particular exemplifications presented hereinabove.

Claims

1. 1. A process for producing a powder comprising lithium oxide and a lithium salt, comprising: heating a mixture of two lithium salts at one or more temperatures ranging from about 50 degrees Celsius below the eutectic point of the mixture of two lithium salts to a temperature below the melting point of the lithium salt having the lower melting point, while removing at least a portion of gaseous by-products produced by the process, to form a powder comprising lithium oxide and a lithium salt; and optionally, a non-reactive additive is present in the mixture of two lithium salts.

2. 2. The process of claim 1, wherein the heating is at one or more temperatures ranging from about 20 degrees Celsius below the eutectic point of the mixture of the two lithium salts to below the melting point of the lithium salt having the lower melting point.

3. 2. The process of claim 1, wherein the two lithium salts are selected from lithium nitrate and lithium bromide, lithium hydroxide and lithium bromide, lithium bromide and lithium carbonate, lithium hydroxide and lithium carbonate, lithium bromide and lithium chloride, and lithium nitrate and lithium iodide.

4. The two lithium salts are lithium nitrate and lithium bromide, and the temperature is in the range of about 178°C to less than about 255°C; lithium hydroxide and lithium bromide, and the temperature is in the range of about 225°C to less than about 470°C; lithium bromide and lithium carbonate, and the temperature is in the range of from about 446°C to less than about 550°C; or lithium hydroxide and lithium carbonate, and the temperature is in the range of about 380°C to less than about 470°C; or 2. The process of claim 1, wherein the catalyst is lithium bromide and lithium chloride and the temperature ranges from about 471°C to less than about 550°C.

5. 5. The process of claim 4, wherein the two lithium salts are lithium hydroxide and lithium carbonate.

6. 6. The process of claim 5, wherein the two lithium salts are lithium hydroxide and lithium carbonate, and the lithium carbonate is formed in situ in the presence of the lithium hydroxide.

7. 6. The process of claim 5, wherein the lithium carbonate is in an amount of about 0.1 wt % to about 20 wt %, based on the total weight of the mixture.

8. 6. The process of claim 5, wherein the temperature ranges from about 380°C to about 460°C.

9. 8. The process of any one of claims 2 to 7, wherein the lithium hydroxide is anhydrous lithium hydroxide.

10. 8. The process of any one of claims 2 to 7, wherein the lithium hydroxide is lithium hydroxide monohydrate.

11. The process of any one of claims 1 to 7, wherein a non-reactive additive is present and is selected from quartz, silica beads, zirconia beads, and lithium oxide.

12. The process of any one of claims 1 to 7, wherein the non-reactive additive is present and is lithium oxide.

13. The process of any of claims 1 to 7, wherein the non-reactive additive is present in an amount of about 1 wt% to about 90 wt%, based on the total weight of the mixture.

14. The process of any of claims 1 to 7, wherein the non-reactive additive is present in an amount of about 20 wt% to about 90 wt% based on the total weight of the mixture.

15. The process of any of claims 1 to 7, wherein the process is carried out in the presence of an inert gas or an oxygen-containing inert gas flowing at a rate of about 25 sccm or greater.

16. 16. The process of claim 15, wherein the inert gas is one or more of helium, nitrogen, and argon.

17. The process of any one of claims 1 to 7, wherein the process is carried out at sub-atmospheric pressure.

18. The process of any one of claims 1 to 7, wherein the process is carried out at a pressure of about 81 kPa or less.

19. 10. The process of claim 1, further comprising heating the powder comprising lithium oxide and lithium carbonate to a temperature ranging from about 25 degrees Celsius below the melting point of lithium carbonate to about 200 degrees Celsius above the melting point of lithium carbonate to form a lithium oxide powder.

20. 1. A process comprising: heating a powder comprising lithium oxide and lithium carbonate at one or more temperatures ranging from about 25 degrees Celsius below the melting point of lithium carbonate to about 200 degrees Celsius above the melting point of lithium carbonate to form a lithium oxide powder.

21. 21. The process of claim 19 or 20, wherein the temperature ranges from about 700°C to about 900°C.

22. 1. A process comprising: heating a powder comprising lithium oxide and a lithium halide at one or more temperatures ranging from about 25 degrees Celsius below the boiling point of the lithium halide to about 200 degrees Celsius above the boiling point of the lithium halide to form a lithium oxide powder.

23. A powder comprising lithium oxide and a lithium salt, wherein the lithium salt is greater than or equal to about 0.1 wt % of the powder.

24. 24. The powder of claim 23 comprising lithium oxide and lithium carbonate, said lithium carbonate being greater than or equal to about 0.3 wt% of said powder.

25. 25. The powder of claim 24, wherein the lithium carbonate is about 0.3 wt% to about 20 wt% of the powder.

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