The invention relates to a preparation method and process of lithium metal

 

 

 

Background technology:

Generally, lithium metal is widely used in lithium batteries, glass, ceramics, alloys, lubricating oil, pharmaceutical and many other industries.

 

The main preparation methods of lithium metal are thermal reduction or electrolysis. Thermal reduction method is not suitable for commercialization due to its economic and technical difficulties. In contrast, lithium metal preparation processes based on electrolysis (i.e., molten salt electrolysis) use lithium chloride as a feedstock and are now widely used commercially.

 

Regarding this, molten salt electrolysis process is known to be a process of separating and recovering high purity lithium metal by electrodeposition of lithium from molten lithium salt (Lic-KCl or Lic-Li2O).

 

Specifically, lithium chloride (licl) and potassium chloride (kcl) mixture after heat treatment and preparation of eutecticmixture, lithium source material lithium chloride into the eutectic salt after melting, the cathode and anode are arranged in the reaction device, and apply a certain current or voltage for electrolysis.

 

In this case, the chloride ion (cl-) contained in the molten salt is oxidized to chlorine gas (Cl 2) at the anode, while the lithium ion (li+) is reduced to lithium metal at the cathode, so that the specific gravity of the reduced lithium is 0.534g/cm3, and it condenses in the upper part of the molten salt in a liquid state.

 

To recover lithium metal in this state, the liquid lithium metal is solidified by cooling it below the melting point of the lithium metal, and then separated from the reaction tank.

 

However, the commonly known preparation method of lithium metal is the method of adding lithium chloride into molten salt, so there are limitations. As the source material, lithium chloride materials can only be prepared by concentration and crystallization after reaction with chlorine gas (cl2) or hydrochloric acid (hcl) (for example, Lithium carbonate (li2co3), lithium oxide (li2o), lithium hydroxide (lioh), etc.).

 

In addition, the resulting lithium metal is easily oxidized by water and oxygen, so it is difficult to use raw materials containing water.

 

At the same time, the heat treatment and cooling of molten salt requires a lot of energy, and the final recovery of lithium metal needs to go through complex steps, so there is a problem of efficiency.