Method for Producing Lithium Oxide

Abstract

A method for the production of lithium oxide and the use of such lithium oxide is described herein. The method includes reacting lithium carbonate with elemental carbon or a carbon source forming elemental carbon under certain reaction conditions. The reaction may be carried out in containers whose product-contacting surfaces are corrosion resistant to the reactants and products. The lithium oxide obtained according to the method described herein can used for the production of pure lithium hydroxide solutions or for the production of glasses glass ceramics or crystalline ceramics, for example, lithium ion conductive ceramics.

Claims

1. A method for the production of powdered lithium oxide from lithium carbonate and elemental carbon or a carbon source forming elemental carbon under the reaction conditions in the temperature range of 720 to 1200 C., characterized in that the reaction takes place under substantial exclusion of oxygen and the reaction is carried out in containers whose product-contacting surfaces are corrosion resistant to the reactants and products.

2. The method according to claim 1, characterized in that the elemental carbon is reacted in the stoichiometric ratio of the lithium carbonate to the carbon of 1:0.5 to 1:1.5.

3. The method according to claim 1, characterized in that the elemental carbon is used in the form of carbon black or activated carbon having a sulfur content of up to 1 weight percent and a silicon content up to 2 weight percent.

4. The method according to claim 1, characterized in that organic materials or organic material mixtures selected from the group consisting of sugar, methane, starch, cellulose, paraffin wax or petroleum are used as a source of elemental carbon.

5. The method according to claim 1, characterized in that the reaction is carried out in reaction vessels whose product-contacted surfaces are consisting of glassy carbon, lithium aluminate or carbon-coated ceramic or C-coated quartz.

6. The method according to claim 5, characterized in that the reaction is carried out in reaction vessels whose product-contacted reaction vessel walls consist of a solidified molten salt.

7. The method according to claim 1, characterized in that the reaction temperature is in the range between 800 and 950 C.

8. The method according to claim 1, characterized in that the reaction is carried out in the pressure range of 0.01 to 2 bar.

9. The method according to claim 1, characterized in that the reaction is carried out in a moving bed reactor.

10. The method according to claim 9, characterized in that the reaction is carried out in a rotary reactor or in a circulating fluidized bed reactor.

11. The use of lithium oxide obtained according to claim 1 for the production of pure lithium hydroxide solution by dissolving the reaction product in water, the amount of water being chosen so that the reaction product lithium hydroxide LiOH has a concentration of at least 8 wt. % and that the insoluble constituents are removed by filtration or centrifugation.

12. The use of lithium oxide obtained according to claim 1 for the production of cathode materials for lithium batteries.

13. The use of lithium oxide obtained according to claim 1 for the production of glasses, glass ceramics or crystalline ceramics.

14. The use of lithium oxide according to claim 13, characterized in that the glasses, glass ceramics or ceramics have a lithium conductivity of at least 10.sup.5 S/cm at room temperature.

Description

EXAMPLE 1: PRODUCTION OF LITHIUM OXIDE BY CARBOTHERMAL DECOMPOSITION OF LITHIUM CARBONATE IN GLASSY CARBON CRUCIBLE

[0018] 8.6 g of Li.sub.2CO.sub.3 (116 mmol) together with 1.4 g of C (Carbon Black N220, 116 mmol C) were filled into a bottle with ISO thread, mixed on the dolly and filled into a crucible made of glassy carbon, the bed height was 0.75 cm.

[0019] The crucible was flushed in a quartz glass tube continuously with 50 l of N.sub.2/h and heated to 900 C. in a tube furnace. After 4 hours, cooling was started.

[0020] The product obtained was: 3.4 g (100% of theory) of weakly gray powder. The total base (acidimetric titration) gave the following result: 66.1 mmol OH.sup./g, corresponding to 98.8% Li.sub.2O. The following contaminants were determined by means of ICP (Inductively Coupled Plasma): 0.50 wt. % Si; 0.35 wt. % S; 0.03 wt. % Na; 0.03 wt. % Ca; 0.005 wt. % Al

[0021] Total Organic Carbon (TOC): 0.1 wt. % C and

[0022] XRD: only reflections for Li.sub.2O.

[0023] Particle size distribution (measurement with Mastersizer 3000 from Malvern Instruments):

[0024] D.sub.10=30 m

[0025] D.sub.50=69 m

[0026] D.sub.90=163 m

[0027] No measurable mass change of the crucible was observed, the weight difference was <0.01 g. The same crucible was used for a further 10 experiments without any microstructural destruction or weight change being observed.

EXAMPLE 2: PRODUCTION OF A PURE AQUEOUS LITHIUM HYDROXIDE SOLUTION FROM LITHIUM OXIDE

[0028] 2.1 g of the product from Example 1 were dissolved in 31.0 g of water and insoluble residue was filtered off. The clear, colorless filtrate was analyzed:

[0029] Total base (acidimetric titration). 4.25 mmol/g corresponding to 10.2 wt. % LiOH (97% of theory)

[0030] Carbonate titration: 0.15 wt. % Li.sub.2CO.sub.3.

[0031] The following contaminants were found by ICP analysis of the solution:

[0032] 8 ppm Fe; Na, K<10 ppm; 60 ppm S; 14 ppm Si

[0033] The purity of the lithium hydroxide formed is about 99.9% (based on LiOH-solid contained).

[0034] Extrapolated to the lithium oxide used, the main contaminants were thus depleted as follows:

[0035] Si: 96%

[0036] S: 73%

Comparative Example 1: Production of Lithium Oxide by Carbothermal Decomposition of Lithium Carbonate in the Alox Crucible

[0037] As in Example 1, a mixture of 8.6 g of lithium carbonate powder and 1.6 g of carbon black, type N220 was reacted at 900 C. to form lithium oxide in a crucible made of Al.sub.2O.sub.3.

[0038] The reaction product contained 0.34 wt. % Al. In comparison, the product produced in the glassy carbon crucible only 0.005 wt. % Al. 0.05 wt. % crucible mass was removed by corrosion. In subsequent experiments similar removal rates were observed. Thus, there is no passivation of the surface.

Comparative Example 2: Production of Lithium Oxide by Carbothermal Decomposition of Lithium Carbonate in the Ti-Lined Crucible

[0039] A titanium foil was placed at the bottom of glassy carbon crucible and a homogenized reaction mixture consisting of 8.6 g of lithium carbonate and 1.6 g of carbon black, type N220, was added on top. The reaction mixture was reacted to form lithium oxide under the same conditions as described in Example 1.

[0040] The foil became white and brittle during the course of the reaction. It already disintegrated at slight mechanical stress and could not be completely separated from the Li.sub.2O formed.