Process for making lithium titanate
A process is provided for making lithium titanate of closely controlled particle size in the range 5 nm to 2000 nm. The process includes re-firing lithium titanate under controlled conditions so that crystallites of the desired particle size are grown. The lithium titanate may be derived from any suitable source. A suitable source of lithium titanate can be from a process that includes evaporation of a blend that contains lithium and titanium to form a mixture containing lithium and titanium compounds that are subsequently calcined to form lithium titanate. The blend of titanium and lithium may be derived from a variety of titanium and lithium precursor materials.
1. A process for producing lithium titanate comprising:
a. preparing a blend comprising titanium and lithium;
b. evaporating the blend to form a mixture of lithium titanium compounds, wherein the evaporating is conducted at a temperature above the boiling point of the liquid in the blend but below the temperature where significant reaction of the lithium and the titanium compounds occurs;
c. calcining the mixture to form lithium titanate having a particle size between about 5 and 2000 nm and having a surface area between about 27 and 400 m 2 /g.
2. The process of claim 1 further comprising crushing the lithium titanate.
3. The process of claim 2 further comprising spray drying the lithium titanate.
4. The process of claim 3 further comprising re-firing the spray dried product.
5. The process of claim 4 wherein the re-firing is conducted at a temperature between about 450° and about 750° C.
6. The process of claim 2 wherein the lithium titanate is crushed to a size smaller or equal to a size of a final lithium titanate product.
7. The process of claim 1 wherein the lithium titanate is washed before being crushed.
8. The process of claim 1 wherein the blend comprises an aqueous solution of titanium and lithium.
9. The process of claim 8 wherein the lithium is provided from a source selected from the group consisting of lithium chloride, lithium oxychloride, lithium nitrate, lithium hydroxide, and mixtures thereof.
10. The process of claim 8 wherein the solution comprises a mixture of titanium oxychloride and lithium chloride.
11. The process of claim 1 wherein the blend comprises a suspension of an amorphous oxidized titanium compound in a solution containing lithium.
12. The process of claim 1 where the evaporation process is conducted in a spray dryer.
13. The process of claim 1 where the evaporation process is conducted at a temperature between about 120° and about 350° C.
14. The process of claim 1 where the calcination process is conducted at a temperature between about 700° and about 900° C.
15. The process of claim 1 wherein the mixture comprises a film of an amorphous oxidized titanium compound and a lithium salt.
16. The process of claim 15 wherein the amorphous oxidized titanium compound is titanium dioxide and wherein the lithium salt is lithium hydroxide.
17. The process of claim 15 wherein the lithium salt is lithium chloride.
18. The process of claim 1 wherein the mixture comprises hollow spheres having a diameter between about 1 and 100 μm.
19. The process of claim 18 wherein the hollow spheres have a membrane thickness between about 30 nanometers and 1000 nanometers.
20. The process of claim 1 wherein the ratio of the amount of lithium to the amount of titanium in the blend (Li/Ti) is between about 0.116 and 0.128.
21. The process of claim 20 wherein the lithium titanate has a phase purity of at least 98% by weight Li 4 Ti 5 O 12 spinel.
22. A Li 4 Ti 5 O 12 formed by the process of claim 4 .
23. The Li 4 Ti 5 O 12 of claim 22 having a particle size between 5 and 2000 nm.
24. A process to produce lithium titanate with a desired particle size between 5 and 2000 nm and a surface area between about 27 and 400 m 2 /g comprising calcining a lithium titanate with a particle size smaller than the desired size, wherein the calcining is conducted at a temperature between about 250° and about 900° C. so as to produce lithium titanate having said desired particle size and said surface area.
25. The process of claim 24 wherein the calcined product is dispersed to liberate crystallites.