SYNTHESIS OF DEEP EUTECTIC SOLVENT CHEMICAL PRECURSORS AND THEIR USE IN THE PRODUCTION OF METAL OXIDES

Abstract

The present invention is directed in a first aspect to a process for forming a deep eutectic solvent chemical precursor. The process includes the steps of providing one or more metal ion donors, preferably one or more salts; providing one or more hydrogen bond donors, and combining the one or more salts with the one or more hydrogen bond donors. The present invention is directed in a second aspect to forming one or more metal oxides by reacting one or more of the deep eutectic solvents of the first aspect of the invention through the application of heat via methods such as flame spray pyrolysis or the application of microwaves.

Claims

1. A process for forming a deep eutectic solvent chemical precursor containing one or more metal ions comprising the steps of: providing one or more salts; providing one or more hydrogen bond donors; and combining said one or more salts with said one or more hydrogen bond donors.

2. The process of claim 1, wherein each of said one or more salts is selected from the group consisting of hydrated metal acetates, hydrated metal nitrates, hydrated metal sulfates, hydrated metal halides, metal acetates, metal nitrates, metal sulfates, metal halides, hydrated metal oxalates, metal oxalates, metal alkoxides, and combinations thereof.

3. The process of claim 1, wherein each of said hydrogen bond donors is selected from the group consisting of glycerol, ethylene glycol, acetamide, urea, and combinations thereof.

4. The process of claim 3, wherein said one or more hydrogen bond donors is glycerol.

5. The process of claim 2, wherein each of said one or more salts is selected from the group consisting of lithium acetate (Li(CH.sub.3COO)), manganese acetate (Mn(CH.sub.3COO).sub.2); cobalt acetate (Co(CH.sub.3COO).sub.2); nickel acetate (Ni(CH.sub.3COO).sub.2); Li(Ni.sub.1/3Mn.sub.1/3Co.sub.1/3)(CH.sub.3COO).sub.2; Li(CH.sub.3COO).2H.sub.2O; Mn(CH.sub.3COO).sub.2.4H.sub.2O; Co(CH.sub.3COO).sub.2.4H.sub.2O; Ni(CH.sub.3COO).sub.2.4H.sub.2O; LiCl; MnCl.sub.2; CoCl.sub.2; NiCl.sub.2; AlCl.sub.3; LiClH.sub.2O; MnCl.sub.2.6H.sub.2O; CoCl.sub.2.6H.sub.2O; NiCl.sub.2.6H.sub.2O; AlCl.sub.3.9H.sub.2O; Ni(NO.sub.3).sub.2, Mn(NO.sub.3).sub.2; Co(NO.sub.3).sub.2; LiNO.sub.3; Zn(NO.sub.3).sub.2; Mn(NO.sub.3).sub.2.4H.sub.2O; Co(NO.sub.3).sub.2.4H.sub.2O; LiNO.sub.3.xH.sub.2O (x=0.5-3); Al(NO.sub.3).sub.3.9H.sub.2O; and combinations thereof.

6. The process of claim 4, wherein the molar ratio of said salt to said glycerol is between 1:1 and 1:10.

7. The process of claim 6, wherein the molar ratio of said salt to said glycerol is between 1:4 and 1:6.

8. The process of claim 7, wherein the molar ratio of said salt to said glycerol is 1:5.

9. The process of claim 1, wherein prior to said combining step, said one or more hydrogen bond donors are heated to reduce their viscosity.

10. The process of claim 9, wherein said one or more hydrogen bond donors are heated to reduce their viscosity by an order of magnitude.

11. The process of claim 9, wherein said combining step comprises constantly stirring said one or more hydrogen bond donors and gradually adding said one or more salts to said one or more hydrogen bond donors.

12. The process of claim 11, further comprising a heating step following said combining step wherein said one or more salts and said one or more hydrogen bond donors are heated to reduce their viscosity.

13. The process of claim 12, wherein following said combining step said one or more salts and said one or more hydrogen bond donors are heated to reduce their viscosity by an order of magnitude.

14. The process of claim 2, wherein said salt is a metal acetate formed by: providing a metal carbonate; providing acetic acid; and reacting said metal carbonate with said acetic acid.

15. A process for forming one or more metal oxides comprising the steps of: providing one or more deep eutectic solvents of claim 1; and reacting said one or more deep eutectic solvents to produce said one or more metal oxides.

16. The process of claim 15, wherein said reaction step comprises flame spray pyrolysis to produce said one or more metal oxides.

17. The process of claim 16, wherein said flame spray pyrolysis is carried out at a temperature between 500 and 2000 degrees Celsius.

18. The process of claim 15, wherein said reaction step comprises microwaving said deep eutectic solvent to produce said one or more metal oxides.

19. The process of claim 15, wherein one or more deep eutectic solvents are provided during said providing step to produce at least one of said metal oxides that includes at least two different metals.

20. The process of claim 15, wherein said metal oxides are in powder form.

21. The process of claim 20, wherein said metal oxides are suitable for use in lithium-ion batteries.

22. The process of claim 15, wherein at least one of said metal oxides is selected from the group consisting of LiCoO.sub.2, LiMn.sub.2O.sub.4, Li.sub.1(NiMnCo).sub.0.33O.sub.2, Li(Ni.sub.0.8Co.sub.0.15Al.sub.0.05)O.sub.2, and combinations thereof.

23. The process of claim 15, wherein at least one of said metal oxides is selected from the group consisting of lithium oxide, cobalt oxide, manganese oxide, nickel oxide, and combinations thereof.

24. The process of claim 15, wherein said reacting step further comprises producing carbon dioxide and water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a photograph of various deep eutectic solvent (DES) chemical precursors in accordance with a first aspect of the present invention.

[0023] FIG. 2 is a photograph of various DES chemical precursors prepared in accordance with a first aspect of the present invention.

[0024] FIG. 3 is an electron microscopy image of a NMC oxide (Li(Ni.sub.1/3Mn.sub.1/3Co.sub.1/3)O.sub.2) powder prepared in a flame spray pyrolysis process in accordance with a second aspect of the present invention.

[0025] FIG. 4 is an electron microscopy image of a NMC oxide (Li(Ni.sub.1/3Mn.sub.1/3Co.sub.1/3)O.sub.2) powder prepared in a microwave process in accordance with a second aspect of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0026] In a first aspect, the present invention is directed to a process for forming a deep eutectic solvent (DES) chemical precursor containing one or more metal ions. The process includes the steps of 1) providing one or more salts, 2) providing one or more hydrogen bond donors, and 3) combining the one or more salts with the one or more hydrogen bond donors.

[0027] The individual components of the DES chemical precursor and their relative concentrations will now be described. Suitable salts include, but are not limited to, hydrated metal acetates, hydrated metal oxalates, hydrated metal nitrates, hydrated metal sulfates, hydrated metal halides, metal acetates, metal oxalates, metal nitrates, metal sulfates, metal halides, metal alkoxides, and combinations thereof. Suitable metal acetates include, but are not limited to, lithium acetate (Li(CH.sub.3COO)), manganese acetate (Mn(CH.sub.3COO).sub.2); cobalt acetate (Co(CH.sub.3COO).sub.2); nickel acetate (Ni(CH.sub.3COO).sub.2); and combinations thereof. Suitable hydrated metal acetates include, but are not limited to, Li(CH.sub.3COO).sub.2H.sub.2O; Mn(CH.sub.3COO).sub.2.4H.sub.2O; Co(CH.sub.3COO).sub.2.4H.sub.2O; Ni(CH.sub.3COO).sub.2.4H.sub.2O; and combinations thereof. Hydrated metal acetates are more preferable than metal acetates. Suitable metal halides include, but are not limited to LiCl, MnCl.sub.2, CoCl.sub.2, NiCl.sub.2, and AlCl.sub.3. Suitable hydrated metal halides include, but are not limited to, LiClH.sub.2O, MnCl.sub.2.6H.sub.2O, CoCl.sub.2.6H.sub.2O, NiCl.sub.2.6H.sub.2O, AlCl.sub.3.9H.sub.2O. Suitable metal nitrates include, but are not limited to: Ni(NO.sub.3).sub.2; Mn(NO.sub.3).sub.2; Co(NO.sub.3).sub.2; LiNO.sub.3; and Al(NO.sub.3).sub.3. Suitable hydrated metal nitrates include, but are not limited to: Ni(NO.sub.3).sub.2.4H.sub.2O; Mn(NO.sub.3).sub.2.4H.sub.2O; Co(NO.sub.3).sub.2.4H.sub.2O; LiNO.sub.3.xH.sub.2O (x=0.5-3) and Al(NO.sub.3).sub.3.9H.sub.2O.

[0028] The one or more hydrogen bond donors serve as complexing agents and are preferably alcohols with three or more carbons. Preferably, the one or more hydrogen bond donors/complexing agents are glycerol and ethylene glycol, acetamide, urea, and combinations thereof. More preferably, the one or more hydrogen bond donors is glycerol.

[0029] The thickness of the DES chemical precursor increases as the molar ratio of the one or more salts to the one or more hydrogen bond donors in the DES chemical precursor increases, and the thickness desired of the DES chemical precursor will depend on the application. Where the one or more hydrogen bond donors is glycerol, the molar ratio of the salt to the glycerol in the DES chemical precursor is preferably between 1:1 and 1:10, more preferably between 1:4 and 1:6, and most preferably is 1:5.

[0030] The process for preparing the DES chemical precursor will now be described in more detail. First, the one or more salts and the one or more hydrogen bond donors/complexing agents to be used are each measured out to pre-determined amounts that will meet the desired molar ratio of the components of the DES chemical precursor. Second, prior to combining the one or more salts and the one or more hydrogen bond donors of the DES chemical precursor, the one or more hydrogen bond donors are preferably heated to reduce the viscosity of the one or more hydrogen bond donors, preferably by an order of magnitude. Preferably, the one or more salts are gradually introduced into the one or more hydrogen bond donors as the one or more hydrogen bond donors are constantly stirred. After the one or more salts and the one or more hydrogen bond donors are combined, they are heated to reduce the viscosity of the DES chemical precursor, preferably by an order of magnitude.

[0031] Where the one or more hydrogen bond donors is glycerol, at low temperatures, for example at room temperature, the DES chemical precursor formation takes much longer, and due to the high viscosity of the combination of the salt and the glycerol, it is hard to mix. At too high of a temperature (greater than 150 degrees Celsius), metal glycerolate can form and precipitate out. In one preferred embodiment, the combination of the one or more salts and the glycerol are heated to a temperature of 100 degrees Celsius for a period of approximately two hours.

[0032] Some salts may not form a DES chemical precursor with one or more hydrogen bond donors without the addition of a third chemical or without first converting the salts to new salts. For example, certain metal carbonates cannot form DES chemical precursors. Specific non-limiting examples include, but are not limited to lithium carbonate. Unlike potassium carbonate, lithium carbonate must first be mixed with acetic acid to convert it to lithium acetate, then mixing the lithium acetate with one or more hydrogen bond donors such as glycerol to form a DES chemical precursor.

[0033] In a second aspect, the present invention is directed to a process for forming one or more metal oxides. Suitable metal oxides include, but are not limited to: lithium oxide, cobalt oxide, manganese oxide, nickel oxide, LiCoO.sub.2, LiMn.sub.2O.sub.4, Li.sub.1(NiMnCo).sub.0.33O.sub.2, Li(Ni.sub.0.8Co.sub.0.15Al.sub.0.05)O.sub.2, and combinations thereof. The process includes the steps of 1) providing one or more deep eutectic solvents of the first aspect of the invention, and 2) reacting the one or more deep eutectic solvent to produce one or more metal oxides. In certain embodiments, carbon dioxide and water are also produced. Generally speaking, the resulting metal oxides are in powder form, in certain aspects nanopowders, and certain metal oxides will be suitable for use in lithium-ion batteries.

[0034] In one embodiment, the reaction step is carried out through flame spray pyrolysis. First, the DES chemical precursor is heated to reduce its viscosity, preferably by an order of magnitude. In one embodiment, the DES chemical precursor is heated to a temperature ranging between 50 and 200 degrees Celsius. In one embodiment, the temperature is 100 degrees Celsius. Second, the DES chemical precursor is sprayed into the reaction chamber. In one embodiment, the flow rate of the DES chemical precursor ranges between 0.1 and 10 gph. The flow rate will depend on the DES chemical precursor used and the size of the spray nozzle. In one embodiment, the temperature of the flame spray reactor ranges between 500 and 2000 degrees Celsius. Preferably, where glycerol is the hydrogen bond donor/complexing agent, the temperature ranges from 800 to 1200 degrees Celsius. Third, after pyrolysis is complete, the metal oxide powders produced are collected downstream.

[0035] While flame spray pyrolysis is preferred, other spray pyrolysis processes can be also be used to obtain metal oxide powders. For example, a high temperature electric furnace can be used to pyrolyze the DES chemical precursors.

[0036] In one embodiment, microwaves are used to heat the precursors to make metal oxide powders. First, the DES chemical precursor is placed in a container, which is then placed in a microwave device. Second, the DES chemical precursor is heated. In one embodiment, the DES chemical precursor is heated for a time ranging from 2 to 30 min at a power ranging between 400 and 800 W to form metal oxide powder.

[0037] Alternatively, other heating mechanisms can be used.

[0038] It should be understood that the process of the second aspect of the invention can be carried out with a DES chemical precursor that includes two or more salts or with two or more DES chemical precursors to produce one or more metal oxides, carbon dioxide, and water. For example:

Li(CH.sub.3COO)+Mn(CH.sub.3COO)+O.sub.2 yields LiMnO.sub.2+CO.sub.2+H.sub.2O

Li(CH.sub.3COO)+Co(CH.sub.3COO)+O.sub.2 yields LiCoO.sub.2+CO.sub.2+H.sub.2O

[0039] The use of organic biomass byproducts as hydrogen bond donors causes the processes of the instant invention to be green chemical processes (known processes are not green). For example, glycerol is a biomass byproduct of biodiesel processing in the transesterification of triglycerides. In 2014, the global biodiesel production was approximately 7.45 billion gallons, which yielded 740 million gallons of crude glycerol. The use of glycerol in the processes of the instant invention will create a new market for the surplus of available glycerol and reduce the overall production cost of metal oxides.

EXAMPLES

[0040] In Examples 1 and 2, described in more detail below, various DES chemical precursors were formed. The preparation of each DES chemical precursor was carried out according to the following steps. First, a pre-determined amount of each of the salts was measured out by weight. Second, a pre-determined amount of the hydrogen bond donor/complexing agent was weighed or measured by volume. In all of the examples, glycerol was used as the hydrogen bond donor/complexing agent. The amounts of the salts and glycerol used were dependent on the desired molar ratio of the salt to the hydrogen bond donor/complexing agent in each DES chemical precursor. Third, the glycerol was placed in a beaker and heated on a heating plate to about 50 degrees Celsius in order to reduce its viscosity by one order of magnitude (from approximately 1400 centipoise (cP) to approximately 140 centipoise (cP). The viscosity was reduced in order to facilitate the mixing of the salts with the glycerol. Fourth, the salts were added gradually to the glycerol in the beaker, under constant stirring with a magnetic stirrer. Fifth, after all of the salt was added to the glycerol in each beaker, the resulting mixture was placed on a heating plate and heated to 100 degrees Celsius in order to reduce the viscosity by approximately another order of magnitude for approximately two hours. Finally, the mixture was taken off of the heating plate and allowed to cool to room temperature. Each DES chemical precursor was a transparent liquid that is capable of remaining in solution for months.

[0041] In Examples 3 and 4, lithium nickel, manganese, and cobalt (NMC) oxide (Li(Ni.sub.1/3Mn.sub.1/3Co.sub.1/3)O.sub.2) powders in accordance with the second aspect of the present invention were prepared from the DES chemical precursors prepared in Example 1 from hydrated metal acetates of the corresponding metals and glycerol.

Example 1: Formation of Deep Eutectic Solvents (DES) Chemical Precursors with Hydrated Metal Acetates

[0042] DES chemical precursors were prepared using the following hydrated metal acetates: Li(CH.sub.3COO).2H.sub.2O; Mn(CH.sub.3COO).sub.2.4H.sub.2O; Co(CH.sub.3COO).sub.2.4H.sub.2O; Ni(CH.sub.3COO).sub.2.4H.sub.2O; and their combinations. Glycerol was used as the hydrogen bond donor/complexing agent and solvent. The DES chemical precursors are shown in FIG. 1. The molar ratio of the salts to the hydrogen bond donor/complexing agents for each of the samples was 1:5. These DES chemical precursors were all fairly thick liquids at room temperature. When heated to over 100 C., they were quite fluid. At this molar ratio, the salt loading of the DES chemical precursor shown at the right that used combinations of the hydrated metal acetates was approximately 43.16 (w/w) %, which is a suitable composition for forming a NMC oxide, more specifically Li(Ni.sub.1/3Mn.sub.1/3Co.sub.1/3)O.sub.2. It is noted that the DES chemical precursor prepared with combinations of the four hydrated metal acetates was formed (on a molar basis) from 3 parts Li(CH.sub.3COO); 1 part Mn(CH.sub.3COO).sub.2; 1 part Co(CH.sub.3COO).sub.2; and 1 part Ni(CH.sub.3COO).sub.2.

Example 2: Formation of Deep Eutectic Solvents (DES) Chemical Precursors with Metal Chloride and Nitrates

[0043] Samples of DES chemical precursors were also prepared using hydrated metal chloride, hydrated metal nitrates, and a metal nitrate. The hydrated metal chloride used was NiCl.sub.2.6H.sub.2O. The hydrated metal nitrates used were Mn(NO.sub.3).sub.2.4H.sub.2O; Co(NO.sub.3).sub.2.4H.sub.2O; and Zn(NO.sub.3).sub.2.6H.sub.2O. The metal nitrate used was LiNO.sub.3. Glycerol was used as the hydrogen bond donor/complexing agent and solvent. The DES chemical precursors are shown in FIG. 2. The molar ratio of the salts to the hydrogen bond donor/complexing agent for each of the samples was 1:5.

Example 3: NMC Oxide Powder Preparation Via Flame Spray Pyrolysis

[0044] The DES chemical precursor prepared in Example 1 from combinations of the hydrated metal acetates and glycerol was used in a flame spray pyrolysis process with an air atomizing nozzle to produce NMC oxide (Li(Ni.sub.1/3Mn.sub.1/3Co.sub.1/3)O.sub.2) powder as follows. First, approximately 100 mL of the DES chemical precursor was heated to 100 degrees Celsius. Second, the DES chemical precursor was sprayed into a reaction chamber at a temperature of approximately 1,500 degrees Celsius where the NMC oxide (Li(Ni.sub.1/3Mn.sub.1/3Co.sub.1/3)O.sub.2) powders were formed. Third, after burning, the metal oxide powders were collected downstream using a bag filter. The morphology of the NMC powder is shown in FIG. 3 in the electron microscopy images, each of which is at a different order of magnification.

Example 4: NMC Oxide Powder Preparation Via Application of Microwaves

[0045] The DES chemical precursor prepared in Example 1 from combinations of the hydrated metal acetates and glycerol was used in a microwave process to produce NMC oxide (Li(Ni.sub.1/3Mn.sub.1/3Co.sub.1/3)O.sub.2) powders as follows. The microwave used was a standard home microwave (800 W). First, 10 mL of the DES chemical precursor was placed in a beaker and placed in the microwave. Second, the DES chemical precursor was heated at full power for 10 minutes to form NMC oxide (Li(Ni.sub.1/3Mn.sub.1/3Co.sub.1/3)O.sub.2) powder. The morphology of the NMC powder is shown in FIG. 4 in the electron microscopy images, each of which is at a different order of magnification.

[0046] From the foregoing it will be seen that this invention is one well adapted to attain all ends and objectives herein-above set forth, together with the other advantages which are obvious and which are inherent to the invention.

[0047] Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matters herein set forth or shown in the accompanying figures are to be interpreted as illustrative, and not in a limiting sense.

[0048] While specific embodiments have been shown and discussed, various modifications may of course be made, and the invention is not limited to the specific forms or arrangement of parts and steps described herein, except insofar as such limitations are included in the following claims. Further, it will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.