Method for preparing high-purity metal lithium by vacuum thermal reduction method

A method for preparing a purified lithium, comprising:

• S1:
• mixing-raw material, a refractory agent, and a catalyst to form a first mixture and briquetting the first mixture,
• thermally decomposing the briquetted first mixture to form an unsaturated composite oxide comprising lithium oxide and the refractory agent, and
• recycling a sublimated and condensed catalyst;
• S2:
• mixing the unsaturated composite oxide, a reducing agent, and a fluxing agent to form a second mixture, and briquetting the second mixture;
• S3:
• reducing the briquetted second mixture in a vacuum reaction furnace to form a gaseous mixture containing solid particles;
• S4:
• passing the gaseous mixture sequentially through a centrifugal filter in a dust chamber of a temperature control device, a first condensing chamber, and a micron ceramic filter to remove more than 99.95% of the solid particles in the gaseous mixture to form a purified gas, wherein each of the centrifugal filter and the first condensing chamber has a temperature of 700-800° C. and a linear gas velocity of 1.2-1.8 m/sec, and a temperature of the purified gas is 650-700° C.;
• S5:
• cooling the purified gas using a cooling liquid at below −100° C. in a condenser in a second condensing chamber to a temperature of 50-80° C. to condense a condensed lithium from the purified gas to obtain a condensed lithium;
• and
• S6:
• subjecting the condensed lithium to one or more selected from flux smelting, refining, purifying by distillation under the protection of Ar to form the purified lithium,
• wherein the catalyst is selected from Sb2O3, Bi2O3, and mixtures thereof.